Citation Nr: 1033840 Decision Date: 09/09/10 Archive Date: 09/21/10 DOCKET NO. 03-12 176A ) DATE ) ) On appeal from the Department of Veterans Affairs Regional Office in San Juan, the Commonwealth of Puerto Rico THE ISSUES 1. Entitlement to service connection for sickle cell trait. 2. Entitlement to service connection for arthritis of the arms, shoulder, ankles, and neck (polyarthritis). 3. Entitlement to service connection for a right shoulder disability. 4. Entitlement to service connection for an acquired psychiatric disorder, to include post-traumatic stress disorder (PTSD). 5. Entitlement to service connection for asbestosis. REPRESENTATION Appellant represented by: Disabled American Veterans ATTORNEY FOR THE BOARD K. Fitch, Counsel INTRODUCTION The Veteran served on active duty from October 1978 to October 1988. This matter comes before the Board of Veterans' Appeals (Board) on appeal from rating decisions of the Department of Veterans Affairs (VA) Regional Office (RO) in Indianapolis, Indiana. The claim has been transferred to the RO in San Juan, the Commonwealth of Puerto Rico. In December 2007, the Veteran testified before the undersigned in Washington, D.C., at a Board hearing. In March 2008, the Board denied entitlement to service connection for tinnitus, anemia, and a split in the abdomen, and remanded the claims of entitlement to service connection for sickle cell trait, arthritis of the arms, shoulder, ankles, and neck, a right shoulder disability, post-traumatic stress disorder (PTSD), and asbestosis for further development and adjudication. This having been completed, the matter has been returned to the Board for further review. As a preliminary matter, the Board finds that the development directed by the March 2008 remand has been completed, and, thus, a new remand is not required in order to comply with the holding of Stegall v. West, 11 Vet. App. 268 (1998). After the most recent supplemental statement of the case dated in December 2009, the Veteran submitted additional evidence. In May 2010, the Veteran's representative waived initial RO consideration of this evidence. The Board will consider this evidence when reviewing the Veteran's claims. The Board notes that the Veteran has been diagnosed with PTSD. The Board also notes that the Veteran has a diagnosis of depressive disorder. The United States Court of Appeals for Veterans Claims (Court) has held that claims for service connection for PTSD encompass claims for service connection for all psychiatric disabilities. Clemons v. Shinseki, 23 Vet. App. 1 (2009) (the scope of a mental health disability claim includes any mental disability that may reasonably be encompassed by the claimant's description of the claim, reported symptoms, and the other information of record). Therefore, the Board has characterized this issue as set forth above. FINDINGS OF FACT 1. The Veteran's sickle cell trait is a hereditary defect that did not manifest as a disease during the Veteran's active duty military service and is not otherwise attributable to her service. 2. The preponderance of the evidence does not demonstrate that polyarthritis and a right shoulder disability are causally or etiologically related to the Veteran's active military service, nor may such conditions be presumed to have been incurred in or aggravated by service. 3. The preponderance of the medical evidence of record does not reflect that the Veteran has a current diagnosis of PTSD. 4. The Veteran's currently diagnosed depressive disorder is not found to be causally or etiologically related to the Veteran's military service. 5. The Veteran does not have a current lung disability or other condition attributable to claimed asbestos exposure in service. CONCLUSIONS OF LAW 1. Service connection for sickle cell trait is not established. 38 U.S.C.A. §§ 1110, 1131, 5103, 5103A, 5107 (West 2002 & Supp. 2009); 38 C.F.R. §§ 3.102, 3.303, 4.9 (2009). 2. Polyarthritis and a right shoulder disability were not incurred in or aggravated by active service, nor may such condition be presumed to have been incurred or aggravated in service. 38 U.S.C.A. §§ 1110, 1131, 5103, 5103A, 5107 (West 2002 & Supp. 2009); 38 C.F.R. §§ 3.303, 3.307, 3.309 (2009). 3. PTSD was not incurred in or aggravated by active service. 38 U.S.C.A. §§ 1110, 1131, 5103, 5103A, 5107 (West 2002 & Supp. 2009); 38 C.F.R. §§ 3.102, 3.159, 3.303, 3.304 (2009). 4. Depressive disorder was not incurred in or aggravated by active service. 38 U.S.C.A. §§ 1110, 1131, 5103, 5103A, 5107 (West 2002 & Supp. 2009); 38 C.F.R. §§ 3.102, 3.159, 3.303, 3.304 (2009). 5. A lung disability or other condition attributable to claimed asbestos exposure was not incurred or aggravated in active service. 38 U.S.C.A. §§ 1110, 1131 (West 2002 & Supp. 2009); 38 C.F.R. §§ 3.102, 3.159, 3.303, 3.304 (2009). REASONS AND BASES FOR FINDINGS AND CONCLUSIONS I. VA's Duties to Notify and Assist. As a preliminary matter, the Board is required to address the Veterans Claims Assistance Act of 2000 ("VCAA") that became law in November 2000. The VCAA provides, among other things, that VA will make reasonable efforts to notify a claimant of the relevant evidence necessary to substantiate a claim for benefits under laws administered by VA. The VCAA also requires VA to assist a claimant in obtaining that evidence. 38 U.S.C.A. §§ 5103, 5103A; 38 C.F.R. § 3.159. With respect to the Veteran's claims, the Board finds that VA has met all statutory and regulatory notice and duty to assist provisions. See 38 U.S.C.A. §§ 5100, 5102, 5103, 5103A, 5106, 5107, 5126; 38 C.F.R. §§ 3.102, 3.156(a), 3.159, 3.326. In this regard, the Board finds that letters dated in November 2004, July 2007, and March 2008 satisfied the duty to notify provisions. 38 U.S.C.A. § 5103(a); 38 C.F.R. § 3.159(b)(1); Quartuccio v. Principi, 16 Vet. App. 183 (2002). The letters notified the Veteran of the evidence and information necessary to substantiate her claims and informed the Veteran of her and VA's respective responsibilities in obtaining such evidence. In addition, the Veteran was provided notice regarding asbestos exposure as required by M21-1, Part VI, para. 7.21. And the Veteran was advised of the pertinent regulations for PTSD based on a personal assault and was afforded ample opportunity to provide evidence from "other" sources to substantiate her claim. See Patton v. West, 12 Vet. App. 272 (1999). In addition to the foregoing, the Board observes that the Veteran's service treatment records, VA treatment records, Social Security Administration disability records, and private medical records have been obtained, to the extent possible. 38 U.S.C.A. § 5103A; 38 C.F.R. § 3.159. The Veteran has had the opportunity to present evidence and argument in support of her claims, to include at the December 2007 Board hearing. The Veteran has also been afforded VA examinations in connection with the claims. As detailed below, VA examinations conducted in October and November 2008 included relevant findings and opinions for resolution of the appellate claims supported by stated rationale, and based upon both evaluation of the Veteran and an accurate understanding of her medical history based on review of her VA claims folder. Further, no inaccuracies or prejudiced is demonstrated regarding these examinations. Accordingly, the Board finds that these examinations are adequate for resolution of this case. Moreover, there is no indication in the record that any additional evidence, relevant to the issues decided herein, is available and not part of the claims file. For the reasons detailed below, the Board concludes, after reviewing all evidence of record, that the preponderance of the evidence is against the Veteran's claims. As such, any questions as to the appropriate disability ratings or effective dates to be assigned to these claims are rendered moot; and no further notice is needed. Dingess/Hartman v. Nicholson, 19 Vet. App. 473 (2006). Since there is no indication that any failure on the part of VA to provide additional notice or assistance reasonably affects the outcome of this case, the Board finds that any such failure is harmless and proceeds with a merits adjudication of the Veteran's claims. Mayfield v. Nicholson, 19 Vet. App. 103 (2005), rev'd on other grounds, 444 F.3d 1328 (Fed. Cir. 2006). II. Service Connection Claims. Applicable law provides that service connection may be granted for a disability resulting from disease or injury incurred in or aggravated by active military service. 38 U.S.C.A. §§ 1110, 1131; 38 C.F.R. §§ 3.303, 3.304. Service connection may also be granted for certain chronic diseases, such as arthritis, when the disease is manifested to a compensable degree within one year of separation from service. 38 U.S.C.A. §§ 1101, 1112, 1113; 38 C.F.R. §§ 3.307, 3.309. In addition, service connection may be granted for any disease diagnosed after discharge, when all of the evidence, including that pertinent to service, establishes that a disease was incurred in service. 38 C.F.R. § 3.303(d). Establishing service connection generally requires (1) evidence of a current disability; (2) evidence of in-service incurrence or aggravation of a disease or injury; and (3) evidence of a nexus between the claimed in-service disease or injury and the present disease or injury. See Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed.Cir.2009); Jandreau v. Nicholson, 492 F.3d 1372, 1376-77 (Fed.Cir.2007); Hickson v. West, 12 Vet. App. 247, 253 (1999); Caluza v. Brown, 7 Vet. App. 498, 506 (1995); see also 38 C.F.R. § 3.303(a). The existence of a current disorder is the cornerstone of a claim for VA disability compensation. See Degmetich v. Brown, 104 F. 3d 1328 (1997) (holding that the VA's and the United States Court of Appeals for Veterans Claims (Court)'s interpretation of sections 1110 and 1131 of the statute as requiring the existence of a present disorder for VA compensation purposes cannot be considered arbitrary and therefore the decision based on that interpretation must be affirmed); see also Gilpin v. West, 155 F.3d 1353 (Fed. Cir. 1998); Brammer v. Derwinski, 3 Vet. App. 223, 225 (1992); Rabideau v. Derwinski, 2 Vet. App. 141, 144 (1992). That a condition or injury occurred in service alone is not enough; there must be disability resulting from that condition or injury. See Rabideau v. Derwinski, 2 Vet. App. 141, 143 (1992). In the absence of proof of a present disability, there can be no valid claim or the grant of the benefit. Id. Under § 3.303(b), an alternative method of establishing the second and/or third Caluza element is through a demonstration of continuity of symptomatology. See Savage v. Gober, 10 Vet. App. 488 (1997); see also Clyburn v. West, 12 Vet. App. 296, 302 (1999). Continuity of symptomatology may be established if a claimant can demonstrate (1) that a condition was "noted" during service; (2) evidence of postservice continuity of the same symptomatology; and (3) medical or, in certain circumstances lay evidence of a nexus between the present disability and the postservice symptomatology. Savage, 10 Vet. App. at 495-96; see Hickson, 12 Vet. App. at 253 (lay evidence of in-service incurrence sufficient in some circumstances for purposes of establishing service connection); 38 C.F.R. § 3.303(b). The provisions concerning continuity of symptomatology do not relieve the requirement that there be some evidence of a nexus to service. For service connection to be established by continuity of symptomatology there must be competent medical or other evidence that relates a current condition to that symptomatology. See Savage 10 Vet. App. at 495-98 (1997). It is the Board's responsibility to evaluate the entire record on appeal. See 38 U.S.C.A. § 7104(a). When there is an approximate balance in the evidence regarding the merits of an issue material to the determination of the matter, the benefit of the doubt in resolving each such issue shall be given to the claimant. 38 U.S.C.A. § 5107(b); 38 C.F.R. § 3.102. In Gilbert v. Derwinski, 1 Vet. App. 49, 53 (1990), the Court of Appeals for Veterans Claims held that an appellant need only demonstrate that there is an "approximate balance of positive and negative evidence" in order to prevail. The Court has also stated, "It is clear that to deny a claim on its merits, the evidence must preponderate against the claim." Alemany v. Brown, 9 Vet. App. 518, 519 (1996), citing Gilbert. A. Sickle Cell Trait Sickle cell trait alone, without a history of directly attributable pathological findings, is not a ratable disability. Here, the Board notes that, under Diagnostic Code 7714, asymptomatic sickle cell anemia, established case in remission, but with identifiable organ impairment, warrants a 10 percent evaluation. The associated Note states that sickle cell trait alone, without a history of directly attributable pathological findings, is not a ratable disability. Cases of symptomatic sickle cell trait are to be forwarded to the Director, Compensation and Pension Service, for consideration under 38 C.F.R. § 3.321(b)(1). See 38 C.F.R. § 4.117, Diagnostic Code 7714. In this case, the service medical records show that the Veteran was noted to have sickle cell trait during service in October 1979. Post-service, a June 1997 medical record questioned whether the Veteran had ever been noted to have sickle cell trait. As it was unclear if the Veteran has any symptomatic sickle cell trait and directly attributable pathological findings, this matter was remanded by the Board in March 2008 so that the Veteran could be afforded a VA examination to make this assessment. The Veteran was provided a VA examination in connection with this claim in November 2008. The examiner indicated that the Veteran's claims file had been reviewed in connection with the examination and report. The Veteran was noted to have served in the Army from 1978 to 1988 as a medical specialist. She was noted to be working as a nurse. The examiner noted that the Veteran was found to have sickle cell trait during an examination in July 1979. The Veteran was noted to have been seen for recurrent urinary tract infections and a hysterectomy in 1998 with improvement in anemia after that. She was also noted to have bone marrow aspirate with a diagnosis of slight mild hyperplasia and normochromic normocytic red blood cells, but with sickle cell prep that showed sickle cell trait. The Veteran, however, denied any complaints of shortness of breath or chest discomfort, and there was no history of sickle cell crisis or bone pains. The Veteran also denied any excessive fatigue, and the examiner stated that there were no admissions for any sickle cell trait related problems. After examination, the Veteran was indicated to have sickle cell trait. This was noted to be a hereditary disease, incidentally diagnosed in service, with no evidence of anemia or any sickle cell crisis. Here, the Board notes that every Veteran shall be taken to have been in sound condition when examined, accepted, and enrolled for service, except as to defects, infirmities, or disorders noted at the time of examination, acceptance, and enrollment. 38 C.F.R. § 3.304(b). A Veteran who served during a period of war, is presumed to be in sound condition when he or she entered into military service except for conditions noted on entrance medical examination. 38 U.S.C.A. §§ 1111, 1132. Where there is "clear and unmistakable" evidence that the injury or disease claimed pre-existed service, the presumption does not attach, and the issue becomes whether the disease or injury was aggravated during service. Id. The question as to whether a hereditary disease always rebuts the presumption of soundness was posed to the General Counsel in 1988, and the General Counsel, referring in its opinion to another opinion issued in 1985, both of which concerned cases involving retinitis pigmentosa, noted that "retinitis pigmentosa and most other diseases of hereditary origin can be incurred or aggravated in service, in the sense contemplated by Congress in title 38." VAOGC 8-88 (Sept. 29, 1988) (reissued as VAOPGCPREC 67-90 (July 18, 1990). The opinion further stated that they can be considered to be incurred in service if their symptomatology did not manifest itself until after entry on duty. The mere genetic or other familial predisposition to develop the symptoms, even if the individual is almost certain to develop the condition at some time in his or her lifetime, does not constitute having the disease. VAOGC 8-88; see also VAOGC 1-85 (Mar. 5, 1985) (reissued as VAOPGCPREC 82-90 (July 18, 1990). In cases where the appellant seeks service connection for a congenital condition, the Board must classify the condition as to whether it is a disease or defect and discuss the presumption of soundness. Quirin v. Shinseki, 22 Vet. App. 390 (2009). In VAOPGCPREC 82-90, the General Counsel held that service connection may be granted for diseases (but not defects) of congenital, developmental or familial origin, and indicated that support for this position could be found in VA regulations themselves, noting that two familial diseases, sickle cell anemia and Huntington's chorea, were included for rating purposes in the Schedule for Rating Disabilities. VAOPGCPREC 82-90, page 4. VA General Counsel has also held that the existence of a hereditary disease under 38 C.F.R. § 3.303(c) does not always rebut the presumption of soundness, and that service connection may be granted for hereditary diseases which either first manifest themselves during service or which preexist service and progress at an abnormally high rate during service. VAOPGCPREC 67-90 (July 18, 1990), 55 Fed. Reg. 43253 (1990). Turning to the question of in-service disease or injury, the Board notes that the Veteran was noted to have sickle cell trait during service in October 1979. Post-service, a June 1997 medical record questioned whether the Veteran had ever been noted to have sickle cell trait. The November 2008 VA examiner, after examining the Veteran and her claims file, diagnosed sickle cell trait. This was noted to be a hereditary disease, incidentally diagnosed in service, with no evidence of anemia or any sickle cell crisis. As noted, Veterans are presumed to have entered service in sound condition as to their health. This presumption attaches only where there has been an induction examination in which the later complained-of disability was not detected. See Bagby v. Derwinski, 1 Vet. App. 225, 227 (1991). The regulation provides expressly that the term "noted" denotes "[o]nly such conditions as are recorded in examination reports," 38 C.F.R. § 3.304(b), and that "[h]istory of preservice existence of conditions recorded at the time of examination does not constitute a notation of such conditions." See Id at (b)(1). In cases where the disease or injury at issue is not noted on the entrance examination, a two-pronged test is for consideration in determining whether the presumption of soundness has been rebutted. First, VA must show by clear and unmistakable evidence that the disease or injury existed prior to service. Second, VA must show by clear and unmistakable evidence that the preexisting disease or injury was not aggravated by service. VAOPGCPREC 3- 2003 (July 16, 2003). See Wagner v. Principi, 370 F.3d 1089 (Fed. Cir. 2004). The Veteran is not required to show that the disease or injury increased in severity during service before VA's duty under the second prong of this rebuttal standard attaches. See id. The Board must follow the precedent opinions of the General Counsel. See 38 U.S.C.A. § 7104(c). In this case, the Veteran is not noted to have had sickle cell trait at service entry. Therefore, the Board finds that the presumption of soundness attaches with respect to the trait at issue. Thus, the burden is on VA to rebut the presumption by clear and unmistakable evidence that the trait was both pre- existing and not aggravated by service. Although, as noted, the Veteran's sickle cell trait is hereditary in nature, the Board finds that the hereditary nature of the condition, in itself, does not constitute clear and unmistakable evidence that the condition preexisted service in that there is no evidence that any manifestations of sickle cell disease were present prior to the Veteran's entrance into service. Therefore, because there is no clear and unmistakable evidence that manifestations of sickle cell disease existed prior to service, the question of whether clear and unmistakable evidence exists to show that sickle cell disease was not aggravated by service is rendered moot. The Board thus, must address whether there were any manifestations of sickle cell disease present in service. As noted above, the Veteran's medical records do not indicate any disease or manifestations attributable to the Veteran's sickle cell trait. The November 2008 VA examiner noted that sickle cell trait was noted in service, but that there was no evidence of anemia or any sickle cell crisis. The Veteran has not been found to have any symptomatic sickle cell trait. In this regard, the Board notes that the United States Court of Appeals for the Federal Circuit (Federal Circuit) has held that lay evidence is one type of evidence that must be considered, and competent lay evidence can be sufficient in and of itself. The Board, however, retains the discretion to make credibility determinations and otherwise weigh the evidence submitted, including lay evidence. See Buchanan v. Nicholson, 451 F.3d 1331, 1335 (Fed. Cir. 2006). This would include weighing the absence of contemporary medical evidence against lay statements. Here, the Board takes note of the fact that the Veteran is a nurse, and therefore her statements will be afforded appropriate probative value. As to the medical opinions provided, to include those of the Veteran, the Board notes that, when faced with conflicting medical opinions, the Board must weigh the credibility and probative value of each opinion, and in so doing, the Board may favor one medical opinion over the other. See Evans v. West, 12 Vet. App. 22, 30 (1998) (citing Owens v. Brown, 7 Vet. App. 429, 433 (1995)). The Board must account for evidence it finds persuasive or unpersuasive, and provide reasons for rejecting material evidence favorable to the claim. See Gabrielson v. Brown, 7 Vet. App. 36, 39-40 (1994). In determining the weight assigned to this evidence, the Board also looks at factors such as the health care provider's knowledge and skill in analyzing the medical data. See Guerrieri v. Brown, 4 Vet. App. 467, 470-71 (1993); see also Black v. Brown, 10 Vet. App. 279, 284 (1997). Further, the Board may not base a decision on its own unsubstantiated medical conclusions but, rather, may reach a medical conclusion only on the basis of independent medical evidence in the record. Hensley v. Brown, 5 Vet. App. 155 (1993). The failure of a physician to provide a basis for his or her opinion also goes to the weight or credibility of the evidence in the adjudication of the merits. See Hernandez-Toyens v. West, 11 Vet. App. 379, 382 (1998). Other factors for assessing the probative value of a medical opinion are the physician's access to the claims file and the thoroughness and detail of the opinion. See Prejean v. West, 13 Vet. 444, 448-9 (2000); see also Nieves-Rodriguez v. Peake, 22 Vet. App. 295 (2008). With the foregoing in mind, the Board concludes that the opinions offered by the Veteran in support of her claim suggest but do not establish that she had symptomatic sickle cell trait in service. The term "disability," as used for VA purposes, refers to a condition resulting in an impairment of earning capacity. See Allen v. Brown, 7 Vet. App. 439, 448 (1995). This distinction between diagnosis and disability is well established in VA law. Cf. 61 Fed. Reg. 20,440, 20,445 (May 7, 1996) (Diagnoses of hyperlipidemia, elevated triglycerides, and elevated cholesterol are actually laboratory results and are not, in and of themselves, disabilities). Therefore, even though the Veteran tested positive for sickle cell trait during service, the Board finds that greater weight should be accorded the VA physician's opinion which shows that the Veteran's hereditary trait did not result in a manifest disorder. See VAOPGCPREC 67-90, supra. In addition, although the Veteran is a nurse, she has not demonstrated expertise in the area of sickle cell disease. In contrast, the November 2008 VA medical examiner, a medical doctor, supported the opinion with the discussion of the medical evidence of record and provided a detailed rationale in support of the opinion. Not only was a definitive opinion proffered by the examiner, but the etiological opinions were supported by a stated rationale. As such, the Board places greater probative weight on the November 2008 VA medical opinion. While service connection may be granted for congenital or hereditary diseases, if initially manifested in or aggravated by service, the most probative medical evidence of record does not support the Veteran's contention that there was incurrence or permanent aggravation of a congenital disease as a result of the Veteran's period of active service. See VAOPGCPREC 82-90 (July 18, 1990); VAOPGCPREC 67- 90 (July 18, 1990). As the medical evidence indicates that symptomatic sickle cell disease did not manifest in service, or for that matter after service, and therefore, the medical evidence of record does not establish that the Veteran's hereditary sickle cell trait was aggravated beyond its normal progression as a result of his period of active service, the preponderance of the evidence is against the service connection claim for sickle cell trait. There is no doubt to be resolved; and service connection is not warranted. See Gilbert, supra. B. Right Shoulder Disability and Arthritis of the Arms, Shoulder, Ankles, and Neck The Veteran has been diagnosed as having polyarthritis. Post- service medical records also show that the Veteran has non- specific densities of the proximal right humerus and the Veteran complains of right shoulder pain. In this case, the Veteran's representative made allegations that the February 2001 VA examination did not include a review of the claims file in order to render an etiological opinion. As such, the Board remanded these issues so that the Veteran could be afforded a VA examination to determine if the current diagnoses are related to service or is arthritis was manifest within one year of service discharge. The February 2001 VA examination report indicated that the Veteran showed normal muscle bulk without any evidence of atrophy. Range of motion at shoulders, elbows, wrists, hands, fingers, hips, knees, ankles, feet, and toes were within normal limits. Manual muscle testing of her bilateral upper and lower extremities was 5/5 with no gross weakness of asymmetry. The Veteran reported mild pain with range of motion of the hips. The Veteran was not assessed as having any arthritis or right shoulder disability. In October 2008, the Veteran was provided an additional VA examination in connection with her claims. The examiner indicated that the Veteran's claims file had been reviewed in connection with the examination. The Veteran reported that she had a history of rheumatoid arthritis, but no gout or lupus. The examiner noted that there was no documentation to support rheumatoid arthritis in the Veteran's claims file, but she was diagnosed with fibromyalgia, polyarthralgia, and poly arthritis. There was no history of dislocation or subluxation to any joints, but the Veteran stated that she could walk less than one block. The Veteran stated that she has no limit on sitting time, but she limits her standing time to approximately five to ten minutes. The Veteran reported pain, weakness, and stiffness in the right shoulder. She reported that she fell out of a truck, landing on her right shoulder, just after boot camp in 1978. She did not seek treatment for this, and the examiner stated that he could not find any record of this in the Veteran's claims file. The Veteran indicated that she did not seek treatment for this pain until she was out of the service. The Veteran also reported having generalized joint pain around 2001. She reported that all of her joints hurt, and she complained of pain, swelling, redness, and heat in all of her joints. After examination, the Veteran was diagnosed with right shoulder impingement, subacromial bursitis, and acromioclavicular joint arthritis. The examiner then stated that he did not see any evidence in the Veteran's claims file of any injury to the right shoulder. He stated that spurring and subacromial impingement are common conditions that are not necessarily related to the Veteran's service. As the Veteran did not seek treatment in service, the examiner stated that he could not find any evidence that this condition is related to her military service. The examiner then stated that he believed that it was less likely than not related to her service. With respect to polyarthritis, the examiner stated that he thoroughly reviewed the Veteran's claims file and did not see any visits or notes regarding her polyarthritis complaints. The Veteran was noted to have been diagnosed with polyarthritis by an outside physician around 2000 or 2001, and that the Veteran had been worked up for rheumatoid arthritis. The examiner explained that the Veteran did not have any serologic markers, but that this was not 100% sensitive or specific for rheumatoid conditions. However, as the Veteran was not noted to have sought treatment for any of these complaints until after 2000, the examiner found that these complaints were less likely than not related to her service and did not manifest within one year after her discharge. The examiner concluded by finding that it was less likely than not that the Veteran's polyarthritis was related to her service or manifested within one year of service. Based on the foregoing, the Board finds that entitlement to service connection is not warranted in this case for a right shoulder disability and arthritis of the arms, shoulder, ankles, and neck. In this case, the VA examiner, that examined the Veteran's claims file in connection with the claims, found that it was less likely than not that these disorders had their onset in service or within one year of service According to Court, "the probative value of medical opinion evidence is based on the medical expert's personal examination of the patient, the physician's knowledge and skill in analyzing the data, and the medical conclusion the physician reaches." Guerrieri v. Brown, 4 Vet. App. 467, 470 (1993). The credibility and weight to be attached to these opinions is within the province of the Board. Id. In this case, the Board finds that the October 2008 medical opinion is most probative in this case. In this regard, the Board notes that the Veteran has contended on her own behalf that her conditions are related to military service. In this regard, the Board notes that lay witnesses are competent to provide testimony or statements relating to symptoms or facts of events that the lay witness observed and is within the realm of his or her personal knowledge, but not competent to establish that which would require specialized knowledge or training, such as medical expertise. Layno v. Brown, 6 Vet.App. 465, 469-70 (1994). Lay evidence may also be competent to establish medical etiology or nexus. Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009). However, "VA must consider lay evidence but may give it whatever weight it concludes the evidence is entitled to" and mere conclusory generalized lay statement that service event or illness caused the claimant's current condition is insufficient to require the Secretary to provide an examination. Waters v. Shinseki, 601 F.3d 1274, 1278 (2010). Additionally, while non-precedential, in a single-judge Memorandum Decision issued by the Court, it was noted that "in the absence of any medical evidence, the record must provide some evidence beyond an appellant's own conclusory statements regarding causation to establish that the appellant suffered from an event, injury or disease in service." Richardson v. Shinseki, No. 08-0357; see also Woehlaert v. Nicholson, 21 Vet. App. 456 (2007) (although the claimant is competent in certain situations to provide a diagnosis of a simple condition such as a broken leg or varicose veins, the claimant is not competent to provide evidence as to more complex medical questions). In the instant case, the Board finds that the question regarding the potential relationship between the Veteran's claimed disabilities and any instance of her military service to be complex in nature. See Woehlaert , supra. However, the Board notes that the Veteran is a nurse and is therefore competent to opine on medical matters. As noted above, as to the medical opinions provided, to include those of the Veteran, the Board notes that, when faced with conflicting medical opinions, the Board must weigh the credibility and probative value of each opinion, and in so doing, the Board may favor one medical opinion over the other. See Evans v. West, 12 Vet. App. 22, 30 (1998) (citing Owens v. Brown, 7 Vet. App. 429, 433 (1995)). The Board must account for evidence it finds persuasive or unpersuasive, and provide reasons for rejecting material evidence favorable to the claim. See Gabrielson v. Brown, 7 Vet. App. 36, 39-40 (1994). In determining the weight assigned to this evidence, the Board also looks at factors such as the health care provider's knowledge and skill in analyzing the medical data. See Guerrieri v. Brown, 4 Vet. App. 467, 470-71 (1993); see also Black v. Brown, 10 Vet. App. 279, 284 (1997). Here, the Board finds that the opinion of the October 2008 medical examiner to be more probative in this case. The examiner is a medical doctor as opposed to a nurse, and had the advantage of examining both the Veteran and her claims file in connection with the opinion and report. In this case, the Board finds that the Veteran's contentions regarding the etiology of her conditions, as well as her allegations of continuity of symptomatology, are outweighed by the competent and probative October 2008 VA medical examiners' findings. In summary, the Board concludes that the preponderance of the evidence is against finding that the Veteran's disabilities are etiologically related to her military service. The Board may not base a decision on its own unsubstantiated medical conclusions but, rather, may reach a medical conclusion only on the basis of independent medical evidence in the record. Hensley v. Brown, 5 Vet. App. 155 (1993). In making this determination, the Board has considered the provisions of 38 U.S.C.A. § 5107(b) regarding benefit of the doubt, but there is not such a state of equipoise of positive and negative evidence to otherwise grant the Veteran's claims. C. An acquired psychiatric disorder, to include PTSD. Service connection may be granted for a disability resulting from disease or injury incurred in or aggravated by service. 38 U.S.C.A. § 1110; 38 C.F.R. § 3.303(a). Service connection may also be granted for any disease diagnosed after discharge, when all of the evidence, including that pertinent to service, establishes that the disease was incurred in service. 38 C.F.R. § 3.303(d). Service connection for PTSD requires (i) medical evidence establishing a diagnosis of the condition, (ii) credible supporting evidence that the claimed in-service stressor occurred, and (iii) a link, established by medical evidence, between current symptomatology and the claimed in-service stressor, is required. See 38 C.F.R. § 3.304(f). In Patton v. West, 12 Vet. App. 272 (1999), the United States Court of Appeals for Veterans Claims (Court) held that special consideration must be given to claims for PTSD based on personal assault. In particular, the Court held that the provisions in M21-1, Part III, 5.14(c), which address PTSD claims based on personal assault are substantive rules which are the equivalent of VA regulations and must be considered. See also YR v. West, 11 Vet. App. 393, 398-99 (1998). For claims involving service connection for PTSD due to personal assault, VA regulations provide, in pertinent part, as follows: (3) If a post-traumatic stress disorder claim is based on in- service personal assault, evidence from sources other than the veteran's service records may corroborate the veteran's account of the stressor incident. Examples of such evidence include, but are not limited to: records from law enforcement authorities, rape crisis centers, mental health counseling centers, hospitals, or physicians; pregnancy tests or tests for sexually transmitted diseases; and statements from family members, roommates, fellow service members, or clergy. Evidence of behavior changes following the claimed assault is one type of relevant evidence that may be found in these sources. Examples of behavior changes that may constitute credible evidence of the stressor include, but are not limited to: a request for a transfer to another military duty assignment; deterioration in work performance; substance abuse; episodes of depression, panic attacks, or anxiety without an identifiable cause; or unexplained economic or social behavior changes. VA will not deny a post- traumatic stress disorder claim that is based on in-service personal assault without first advising the claimant that evidence from sources other than the veteran's service records or evidence of behavior changes may constitute credible supporting evidence of the stressor and allowing him or her the opportunity to furnish this type of evidence or advise VA of potential sources of such evidence. VA may submit any evidence that it receives to an appropriate medical or mental health professional for an opinion as to whether it indicates that a personal assault occurred. 38 C.F.R. § 3.304(f) (2008). The evidence necessary to establish the occurrence of a stressor during service to support a diagnosis of PTSD will vary depending upon whether the veteran engaged in "combat with the enemy" as established by official records, including recognized military combat citations, or other supportive evidence. If the VA determines that the veteran engaged in combat with the enemy and the alleged stressor is combat-related, then the veteran's lay testimony or statement is accepted as conclusive evidence of the stressor's occurrence and no further development or corroborative evidence is required, provided that such testimony is found to be "satisfactory," i.e., credible, and "consistent with the circumstances, conditions or hardships of service." See 38 U.S.C.A. § 1154(b); 38 C.F.R. § 3.304(f); Dizoglio v. Brown, 9 Vet. App. 163, 164 (1996); West v. Brown, 7 Vet. App. 70, 76 (1994); Zarycki v. Brown, 6 Vet. App. 91, 98 (1993). If, however, the VA determines that the veteran did not engage in combat with the enemy or that the veteran engaged in combat with the enemy, but the alleged stressor is not combat-related, the veteran's lay testimony, by itself, is insufficient to establish the occurrence of the alleged stressor. Instead, the record must contain credible supporting evidence that corroborates the veteran's statements or testimony. Cohen v. Brown, 10 Vet. App. 128, 142 (1993). Prior to July 13, 2010, VA had generally required that, where a determination is made that the Veteran did not "engage in combat with the enemy," or the claimed stressor is not related to combat, the Veteran's lay testimony alone will not be enough to establish the occurrence of the alleged stressor. See Moreau v. Brown, 9 Vet. App. 389, 395 (1996); Dizoglio v. Brown, 9 Vet. App. 163, 166 (1996). In such cases, the record must contain service records or other statements as to the occurrence of the claimed stressor. See West (Carlton) v. Brown, 7 Vet. App. 70, 76 (1994); Zarycki v. Brown, 6 Vet. App. 91, 98 (1993). However, effective July 13, 2010, VA has amended its adjudication regulations governing service connection for PTSD by liberalizing, in certain circumstances, the evidentiary standard for establishing the required in-service stressor. Specifically, the final rule amends 38 C.F.R. § 3.304(f) by redesignating current paragraphs (f)(3) and (f)(4) as paragraphs (f)(4) and (f)(5), respectively, and by adding a new paragraph (f)(3) that reads as follows: (f)(3) If a stressor claimed by a Veteran is related to the Veteran's fear of hostile military or terrorist activity and a VA psychiatrist or psychologist, or a psychiatrist or psychologist with whom VA has contracted, confirms that the claimed stressor is adequate to support a diagnosis of [PTSD] and that the Veteran's symptoms are related to the claimed stressor, in the absence of clear and convincing evidence to the contrary, and provided the claimed stressor is consistent with the places, types, and circumstances of the Veteran's service, the Veteran's lay testimony alone may establish the occurrence of the claimed in-service stressor. For purposes of this paragraph, "fear of hostile military or terrorist activity" means that a Veteran experienced, witnessed, or was confronted with an event or circumstance that involved actual or threatened death or serious injury, or a threat to the physical integrity of the Veteran or others, such as from an actual or potential improvised explosive device; vehicle-imbedded explosive device; incoming artillery, rocket, or mortar fire; grenade; small arms fire, including suspected sniper fire; or attack upon friendly military aircraft, and the Veteran's response to the event or circumstance involved a psychological or psycho-physiological state of fear, helplessness, or horror. The provisions of this amendment apply to applications for service connection for PTSD that are received by VA on or after July 13, 2010; were received by VA before July 13, 2010 but have not been decided by a VA regional office as of July 13, 2010; are appealed to the Board on or after July 13, 2010; were appealed to the Board before July 13, 2010 but have not been decided by the Board as of July 13, 2010; or are pending before VA on or after July 13, 2010 because the United States Court of Appeals for Veterans Claims vacated a Board decision on an application and remanded it for readjudication. 75 Fed. Reg. 39,843 (July 13, 2010), with correcting amendments at 75 Fed. Reg. 41,092 (July 15, 2010). As the Veteran's claim was appealed to the Board before July 13, 2010, but had not been decided by the Board as of July 13, 2010, the amended regulations apply to the instant claim. Once the claimed stressor has been verified, the Veteran's personal exposure to the event may be implied by the evidence of record. A Veteran need not substantiate his actual presence during the stressor event; the fact that the Veteran was assigned to and stationed with a unit that was present while such an event occurred strongly suggests that he was, in fact, exposed to the stressor event. See Pentecost v. Principi, 16 Vet. App. 124 (2002); Suozzi v. Brown, 10 Vet. App. 307 (1997). When there is an approximate balance of positive and negative evidence regarding any issue material to the determination of a matter, the Secretary shall give the benefit of the doubt to the claimant. 38 U.S.C.A. § 5107; 38 C.F.R. § 3.102; see also Gilbert v. Derwinski, 1 Vet. App. 49, 53 (1990). In this case, a February 2001 VA examination diagnosed the Veteran as having a depressive disorder and PTSD, but there was no chart available for review. Thereafter, medical evidence showed that the Veteran might not have PTSD. Based on the foregoing, the Board, in March 2008, remanded this matter so that the Veteran could be afforded a new examination which included a review of the claims file. The examiner was asked to resolve whether or not the Veteran has PTSD and provide the etiological basis for that diagnosis. In November 2008, the Veteran was provided a VA examination in connection with her claim. The examiner indicated that the Veteran's claims file had been thoroughly reviewed in connection with the examination. The examiner indicated that this review took approximately 5 hours and included the Veteran's electronic medical records as well. The examiner also indicated that he interviewed the Veteran for almost an hour and a half. The Veteran's medical history was noted in the report, including the Veteran's many serious medical conditions. In service, the Veteran was noted to have been seen in 1984 for anxiety, but there was no mention of a sexual assault that the Veteran reported took place in 1978. In this regard, the examiner indicated that the Veteran had given numerous and contradictory accounts of an assault by a drill instructor(s) or sergeant(s). The Veteran was noted to have tested positive for marijuana that led to an Article 15 and an honorable discharge from the military. During this process, the Veteran was noted to have taken an overdose of medication in a suicide attempt and was hospitalized briefly. She was given a discharge diagnosis of adjustment disorder. Prior to this the Veteran was noted to have had numerous excellent performance evaluations. After service, the Veteran claimed PTSD-like symptoms (nightmares) after she underwent surgery for a brain tumor in 1998. In interviewing the Veteran, the Veteran reported various symptoms and complaints. She reported that she was mistreated in the military, including sexual mistreatment and assault from her drill instructors and other superiors. The Veteran also reported a consensual sexual relationship with a superior officer in whom she confided. The Veteran's family history was also noted, including longstanding sexual abuse from her father when she was a child. After examination, the Veteran was diagnosed with major depression, recurrent. While the Veteran was noted by the examiner to have been sexually victimized by unscrupulous men in authority, the examiner found that this was not traumatic in the usual sense of a PTSD-associated trauma that results on a threat of death, serious injury, or threat of physical integrity. The examiner stated that the Veteran did not endorse such traumatic event. The examiner also noted that the Veteran's reports were contradictory, ranging from being raped to being seduced. The Veteran's reported nightmares after the 1998 surgery were also found to be thematically unrelated to a traumatic sexual relationship. In this regard, the examiner noted that these nightmares did not include the alleged perpetrator of the sexual trauma. In conclusion, the examiner stated that there was not sufficient evidence to warrant a diagnosis of military-related PTSD. In June 2008, the Veteran submitted the statement of a Vet Center psychologist regarding her claim for PTSD. The Veteran reported that she had been sexually harassed in service by three sergeants and, after reporting this to her superior, reported that she was sexually harassed by him. The psychologist indicated that there was no direct evidence of military sexual trauma, but pointed to several pieces of evidence that he indicated were markers that such sexual trauma had occurred. These included a history of moving duty stations and failing to complete courses, treatment for pelvic pain and related complaints in service, and a short marriage and quick divorce to another soldier in service. This psychologist opined that is was more likely than not that the Veteran experienced military sexual trauma. The Veteran was also diagnosed with PTSD secondary to military sexual trauma. With respect to other psychiatric disabilities, as noted above, the Veteran has been diagnosed with major depression in both the February 2001 and November 2008 VA examinations. The February 2001 VA examiner indicated that the Veteran's claims file had not been reviewed in connection with the examination and also did not provide a nexus opinion regarding the Veteran's psychiatric diagnoses. The November 2008 examiner, on the other hand, specifically indicated that the Veteran's claims file had been reviewed in connection with the examination, as more fully explained above. After examining the Veteran and her claims file in connection with her claim, the examiner found that the Veteran's chronic major depression appeared to have started well after she was discharged from the service. The November 2008 VA examiner also submitted an addendum to the November 2008 report dated in January 2009. In this addendum, he clarified that it was not at all likely that the Veteran's major depression, that started many years after service, was causally related to events that happened to her during the time that she was in the military. Based on the foregoing, the Board finds that entitlement to service connection is not warranted in this case for PTSD or major depression. In this case, after a thorough review of the Veteran's claims file and an examination of the Veteran, the November 2008 VA examiner did not find that the Veteran had a diagnosis of military-related PTSD. And without a current diagnosis of this disability, service connection is not available. As noted above, the existence of a current disorder is the cornerstone of a claim for VA disability compensation. See Degmetich v. Brown, 104 F. 3d 1328 (1997) (holding that the VA's and the United States Court of Appeals for Veterans Claims (Court)'s interpretation of sections 1110 and 1131 of the statute as requiring the existence of a present disorder for VA compensation purposes cannot be considered arbitrary and therefore the decision based on that interpretation must be affirmed); see also Gilpin v. West, 155 F.3d 1353 (Fed. Cir. 1998); Brammer v. Derwinski, 3 Vet. App. 223, 225 (1992); Rabideau v. Derwinski, 2 Vet. App. 141, 144 (1992). That a condition or injury occurred in service alone is not enough; there must be disability resulting from that condition or injury. See Rabideau v. Derwinski, 2 Vet. App. 141, 143 (1992). In the absence of proof of a present disability, there can be no valid claim or the grant of the benefit. Id. In this regard, the Board notes that the Veteran was diagnosed in February 2001 with PTSD. And the June 2008 opinion from the Vet Center psychologist also found that the Veteran had PTSD that was military-related. According to Court, "the probative value of medical opinion evidence is based on the medical expert's personal examination of the patient, the physician's knowledge and skill in analyzing the data, and the medical conclusion the physician reaches." Guerrieri v. Brown, 4 Vet. App. 467, 470 (1993). The credibility and weight to be attached to these opinions is within the province of the Board. Id. In this case, the Board finds that the November 2008 medical opinion, based as it was on an examination of the Veteran and the Veteran's claims file, is most probative in this case. This examiner thoroughly reviewed the Veteran's medical records and examined the Veteran in connection with the claim. The February 2001 examiner, by contrast, indicated that there was no chart available for review. And the June 2008 psychologist also did not indicate a review of the Veteran's records in connection with his opinion. This psychologist noted that there was no direct evidence of military sexual trauma in the Veteran's case, but based his opinion on other indirect markers. Next, with respect to the Veteran's diagnosed major depression, the November 2008 VA examiner, that examined the Veteran and her claims file in connection with the claim, found that this condition started well after service and was not causally related to her military service. Service connection for this disorder is therefore also not warranted in this case. Finally, the Board notes that the Veteran has contended on her own behalf that she has a psychiatric disability, specifically PTSD, that is related to mistreatment she received in the military. In this regard, the Board notes that lay witnesses are competent to provide testimony or statements relating to symptoms or facts of events that the lay witness observed and is within the realm of his or her personal knowledge, but not competent to establish that which would require specialized knowledge or training, such as medical expertise. Layno v. Brown, 6 Vet.App. 465, 469-70 (1994). Lay evidence may also be competent to establish medical etiology or nexus. Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009). However, "VA must consider lay evidence but may give it whatever weight it concludes the evidence is entitled to" and mere conclusory generalized lay statement that service event or illness caused the claimant's current condition is insufficient to require the Secretary to provide an examination. Waters v. Shinseki, 601 F.3d 1274, 1278 (2010). Additionally, while non-precedential, in a single-judge Memorandum Decision issued by the Court, it was noted that "in the absence of any medical evidence, the record must provide some evidence beyond an appellant's own conclusory statements regarding causation to establish that the appellant suffered from an event, injury or disease in service." Richardson v. Shinseki, No. 08-0357; see also Woehlaert v. Nicholson, 21 Vet. App. 456 (2007) (although the claimant is competent in certain situations to provide a diagnosis of a simple condition such as a broken leg or varicose veins, the claimant is not competent to provide evidence as to more complex medical questions). In the instant case, the Board finds that the question regarding whether the Veteran has PTSD that is related to her service is complex in nature. See Woehlaert , supra. However, the Board notes that the Veteran is a nurse and is therefore competent to opine on medical matters. As noted above, as to the medical opinions provided, to include those of the Veteran, the Board notes that, when faced with conflicting medical opinions, the Board must weigh the credibility and probative value of each opinion, and in so doing, the Board may favor one medical opinion over the other. See Evans v. West, 12 Vet. App. 22, 30 (1998) (citing Owens v. Brown, 7 Vet. App. 429, 433 (1995)). The Board must account for evidence it finds persuasive or unpersuasive, and provide reasons for rejecting material evidence favorable to the claim. See Gabrielson v. Brown, 7 Vet. App. 36, 39-40 (1994). In determining the weight assigned to this evidence, the Board also looks at factors such as the health care provider's knowledge and skill in analyzing the medical data. See Guerrieri v. Brown, 4 Vet. App. 467, 470-71 (1993); see also Black v. Brown, 10 Vet. App. 279, 284 (1997). Here, the Board finds that the opinion of the November 2008 medical examiner to be more probative in this case. The examiner is a board certified psychiatrist, as opposed to a nurse, and had the advantage of examining both the Veteran and her claims file in connection with the opinion and report. The Veteran is also not noted to have any specific specialization in psychiatric matters. In this case, the Board finds that the Veteran's contentions regarding the etiology of her conditions, as well as her allegations of continuity of symptomatology, are outweighed by the competent and probative November 2008 VA medical examiners' findings. In summary, the Board concludes that the preponderance of the evidence is against finding that the Veteran has PTSD that is related to her military service. The Board may not base a decision on its own unsubstantiated medical conclusions but, rather, may reach a medical conclusion only on the basis of independent medical evidence in the record. Hensley v. Brown, 5 Vet. App. 155 (1993). In making this determination, the Board has considered the provisions of 38 U.S.C.A. § 5107(b) regarding benefit of the doubt, but there is not such a state of equipoise of positive and negative evidence to otherwise grant the Veteran's claims. E. Asbestosis As to claims of service connection for asbestosis or other asbestos-related diseases, the Board notes that VA has issued a circular on asbestos-related diseases. This circular, DVB Circular 21-88-8, Asbestos-Related Diseases (May 11, 1988) (DVB Circular), provides guidelines for considering compensation claims based on exposure to asbestos. The information and instructions from the DVB Circular were included in a VA Adjudication Procedure Manual, M21-1 (M21- 1), Part VI, para. 7.68 (Sept. 21, 1992). Subsequently, the M2-1 provisions regarding asbestos exposure were amended. The new M21-1 guidelines were set forth at M21-1, Part VI, para. 7.21 (Oct. 3, 1997). The guidelines provide, in part, that the clinical diagnosis of asbestosis requires a history of exposure and radiographic evidence of parenchymal disease; that VA is to develop any evidence of asbestos exposure before, during and after service; and that a determination must be made as to whether there is a relationship between asbestos exposure and the claimed disease, keeping in mind the latency period and exposure information. See Ashford v. Brown, 10 Vet. App. 120 (1997); McGinty v. Brown, 4 Vet. App. 428 (1993). The applicable section of Manual M21-1 also notes that some of the major occupations involving exposure to asbestos include mining, milling, work in shipyards, carpentry and construction, manufacture and servicing of friction products such as clutch facings and brake linings, manufacture and installation of roofing and flooring materials, asbestos cement and pipe products, military equipment, etc. High exposure to respirable asbestos and a high prevalence of disease have been noted in insulation and shipyard workers, and this is significant considering that, during World War II, U.S. Navy Veterans were exposed to chrysotile, amosite, and crocidolite that were used extensively in military ship construction. Furthermore, it was revealed that many of these shipyard workers had only recently come to medical attention because the latent period for asbestos- related diseases varies from 10 to 45 or more years between first exposure and development of disease. Also of significance is that the exposure to asbestos may be brief (as little as a month or two) or indirect (bystander disease). See Department of Veterans Affairs, Veteran's Benefits Administration, Manual M21- 1, Part 6, Chapter 7, Subchapter IV, § 7.21 b. In Dyment v. West, 13 Vet. App. 141, 145 (1999), the Court found that provisions in former paragraph 7.68 (predecessor to paragraph 7.21) of VBA Manual M21-1, Part VI, did not create a presumption of exposure to asbestos. Medical nexus evidence is required in claims for asbestos related disease related to alleged asbestos exposure in service. VAOPGCPREC 4-00. In short, with respect to claims involving asbestos exposure, VA must determine whether or not military records demonstrate evidence of asbestos exposure during service, develop whether or not there was pre-service and/or post-service occupational or other asbestos exposure, and determine whether there is a relationship between asbestos exposure and the claimed disease. See M21-1, Part VI, 7.21; DVB Circular 21- 88-8, Asbestos-Related Diseases (May 11, 1988). Thus, VA must analyze the Veteran's claim of entitlement to service connection for asbestosis under these administrative protocols using the following criteria. Ennis v. Brown, 4 Vet. App. 523, 527 (1993). As noted, the latency period for asbestos-related diseases varies from 10 to 45 or more years between first exposure and development of disease. M21-1, Part VI, 7.21(b)(2), p. 7-IV- 3 (January 31, 1997). An asbestos-related disease can develop from brief exposure to asbestos. Id. M21-1, Part VI, para. 7.21 contains guidelines for the development of asbestos exposure cases. Part (a) in essence acknowledges that inhalation of asbestos fibers can result in fibrosis and tumors, and produce pleural effusions and fibrosis, pleural plaques, mesotheliomas of the pleura and peritoneum, and cancer of the lung, gastrointestinal tract, larynx, pharynx and urogenital system (except the prostate), with the most common resulting disease being interstitial pulmonary fibrosis (asbestosis). Also noted is the increased risk of bronchial cancer in individuals who smoke cigarettes and have had prior asbestos exposure. M21-1, Part VI, para. 7.21(b) pertains to occupational exposure, and acknowledges that high exposure to asbestos and a high prevalence of disease have been noted in insulation and shipyard workers. Noted is that the latent period varies from 10-to-45 or more years between first exposure and development of disease. Also of significance is that the exposure to asbestos may be brief (as little as a month or two) or indirect (bystander disease). M21-1, Part VI, para. 7.21(c) provides that the clinical diagnosis of asbestosis requires a history of exposure and radiographic evidence of parenchymal lung disease. M21-1, Part VI, para. 7.21(d) provides that VA must determine whether military records demonstrate evidence of asbestos exposure in service; whether there is pre-service and/or post-service evidence of occupational or other asbestos exposure; and then make a determination as to the relationship between asbestos exposure and the claimed diseases, keeping in mind the latency and exposure information pertinent to the Veteran. In this case, the Board, in March 2008, found that the record showed that the RO had not complied with M21-1 procedures. The Veteran had not been sent the appropriate letter regarding alleged asbestos exposure. In addition, the Board found that, in the event that it is determined that the Veteran had a documented history of probable asbestos exposure during service, the Veteran should be afforded a VA examination, and the examiner should opine if the Veteran currently has a respiratory disability which is attributable to service to include probable asbestos exposure during service. In March 2008, the Veteran was sent a letter outlining the notice requirement for an Asbestos claim and forwarding to the Veteran a questionnaire regarding this claim. The Veteran was also provided a VA examination in connection with her claim dated in November 2008. The examiner indicated that the Veteran's claims file had been reviewed in connection with the examination and report. Regarding asbestos exposure, the Veteran reported that, in 1978, a group of soldiers was asked to remove some products out of a building. She remembered that they were told that these products had asbestos in them. The examiner noted that there was no documentation of this in the Veteran's claims file, and the Veteran also reported that there was no way that this could be proved. The Veteran also reported that she had a tumor in her nose that was removed in Puerto Rico. She stated that she was told by the physician that this could have had a relation to asbestos exposure. The examiner stated that there were no details regarding this that could be found, with the exception of a pituitary tumor noted in the Veteran's records. The Veteran also reported that she had a brain tumor that could be related to asbestos exposure. Otherwise, the Veteran denied any respiratory distress, and no wheezing or recurrent chest infections. The Veteran never used oxygen or any inhalers. After examination, the Veteran was not diagnosed with any lung disability or other disability related to asbestos exposure. The Veteran's respiratory testing was indicated to be normal and, based on the results, the examiner stated that "I am of the opinion that the Veteran does not have restrictive lung disease which would be expected in asbestosis. Hence there is no lung sequale from the exposure she claims." In addition, the examiner stated that the malignancy that the Veteran mentioned was not in any way related to asbestos exposure based on existing evidence in the literature. Based on the foregoing, the Board finds that the Veteran does not have a current lung disability or other condition attributable to claimed asbestos exposure in service. And, as noted above, the existence of a current disorder is the cornerstone of a claim for VA disability compensation. See Degmetich v. Brown, 104 F. 3d 1328 (1997) (holding that the VA's and the United States Court of Appeals for Veterans Claims (Court)'s interpretation of sections 1110 and 1131 of the statute as requiring the existence of a present disorder for VA compensation purposes cannot be considered arbitrary and therefore the decision based on that interpretation must be affirmed); see also Gilpin v. West, 155 F.3d 1353 (Fed. Cir. 1998); Brammer v. Derwinski, 3 Vet. App. 223, 225 (1992); Rabideau v. Derwinski, 2 Vet. App. 141, 144 (1992). That a condition or injury occurred in service alone is not enough; there must be disability resulting from that condition or injury. See Rabideau v. Derwinski, 2 Vet. App. 141, 143 (1992). In the absence of proof of a present disability, there can be no valid claim or the grant of the benefit. Id. In addition, according to Court, "the probative value of medical opinion evidence is based on the medical expert's personal examination of the patient, the physician's knowledge and skill in analyzing the data, and the medical conclusion the physician reaches." Guerrieri v. Brown, 4 Vet. App. 467, 470 (1993). The credibility and weight to be attached to these opinions is within the province of the Board. Id. In this case, the Board finds that the November 2008 medical opinion, based as it was on an examination of the Veteran and a review of the claims file, is most probative in this case. In this regard, the Board notes that the Veteran has contended on her own behalf that she has a disability related to claimed asbestos exposure in service. In this regard, the Board notes that lay witnesses are competent to provide testimony or statements relating to symptoms or facts of events that the lay witness observed and is within the realm of his or her personal knowledge, but not competent to establish that which would require specialized knowledge or training, such as medical expertise. Layno v. Brown, 6 Vet.App. 465, 469-70 (1994). Lay evidence may also be competent to establish medical etiology or nexus. Davidson v. Shinseki, 581 F.3d 1313, 1316 (Fed. Cir. 2009). However, "VA must consider lay evidence but may give it whatever weight it concludes the evidence is entitled to" and mere conclusory generalized lay statement that service event or illness caused the claimant's current condition is insufficient to require the Secretary to provide an examination. Waters v. Shinseki, 601 F.3d 1274, 1278 (2010). Additionally, while non-precedential, in a single-judge Memorandum Decision issued by the Court, it was noted that "in the absence of any medical evidence, the record must provide some evidence beyond an appellant's own conclusory statements regarding causation to establish that the appellant suffered from an event, injury or disease in service." Richardson v. Shinseki, No. 08-0357; see also Woehlaert v. Nicholson, 21 Vet. App. 456 (2007) (although the claimant is competent in certain situations to provide a diagnosis of a simple condition such as a broken leg or varicose veins, the claimant is not competent to provide evidence as to more complex medical questions). In the instant case, the Board finds that the question regarding the existence of a potential disability related to alleged asbestos exposure is complex in nature. See Woehlaert , supra. However, the Board notes that the Veteran is a nurse and is therefore competent to opine on medical matters. As noted above, as to the medical opinions provided, to include those of the Veteran, the Board notes that, when faced with conflicting medical opinions, the Board must weigh the credibility and probative value of each opinion, and in so doing, the Board may favor one medical opinion over the other. See Evans v. West, 12 Vet. App. 22, 30 (1998) (citing Owens v. Brown, 7 Vet. App. 429, 433 (1995)). The Board must account for evidence it finds persuasive or unpersuasive, and provide reasons for rejecting material evidence favorable to the claim. See Gabrielson v. Brown, 7 Vet. App. 36, 39-40 (1994). In determining the weight assigned to this evidence, the Board also looks at factors such as the health care provider's knowledge and skill in analyzing the medical data. See Guerrieri v. Brown, 4 Vet. App. 467, 470-71 (1993); see also Black v. Brown, 10 Vet. App. 279, 284 (1997). Here, the Board finds that the opinion of the November 2008 medical examiner to be more probative in this case. The examiner is a medical doctor as opposed to a nurse, and had the advantage of examining both the Veteran and her claims file in connection with the opinion and report. In this case, the Board finds that the Veteran's contentions regarding her conditions are outweighed by the competent and probative November 2008 VA medical examiners' findings. In summary, the Board concludes that the preponderance of the evidence is against finding that the Veteran has a disability related to purported asbestos exposure in service. The Board may not base a decision on its own unsubstantiated medical conclusions but, rather, may reach a medical conclusion only on the basis of independent medical evidence in the record. Hensley v. Brown, 5 Vet. App. 155 (1993). In making this determination, the Board has considered the provisions of 38 U.S.C.A. § 5107(b) regarding benefit of the doubt, but there is not such a state of equipoise of positive and negative evidence to otherwise grant the Veteran's claim. ORDER Service connection for sickle cell trait is denied. Service connection for arthritis of the arms, shoulder, ankles, and neck is denied. Service connection for a right shoulder disability is denied. Service connection for an acquired psychiatric disorder, to include PTSD and depressive disorder, is denied. Service connection for asbestosis is denied. ____________________________________________ John Kitlas Acting Veterans Law Judge, Board of Veterans' Appeals Department of Veterans Affairs