Whole Health care for the gastrointestinal (GI) tract may involve the use of an array of diagnostic labs. This Whole Health tool describes a number of laboratory tests. Some of these are quite familiar to clinicians, but others may not be. You are encouraged to learn more about them and decide if they have relevance to your practice or self-care.
More Commonly Used Tests
- Stool for blood (guaiac): Still one of the most useful tests for GI health. Blood in a stool sample, warrants further evaluation for infection or tumor.
- Fecal leukocytes: If positive, think of an infectious process and culture the stool. Doing stool cultures with negative fecal leukocytes is of low yield.
- Stool for ova and parasites: Low yield if no recent travel.
- Giardia antigen and cryptosporidium antigen: These two pathogens may contribute to abnormal bowel function.
- H. pylori testing:
- Checking the serum for antibody will likely always be positive if a person has ever had any exposure during their lifetime. It stays positive even after treatment.
- To check for cure after treatment, tests that will change include:
- Stool H. Pylori antigen
- Urea breath test (better sensitivity and specificity than stool antigen ) can be used to check for cure after treatment.
- Diagnosing H. pylori should be based on local guidelines, when available, given that recommendations may vary based on the prevalence of H. pylori in a population
- Hydrogen breath test: This test generally is done in the Pulmonary or GI departments. It is most useful to detect small intestinal bacterial overgrowth (SIBO). The individual drinks a glucose solution. If there are bacteria in the small intestine, they will ferment the sugar, which results in a larger ratio of hydrogen gas that is measured in exhaled air. However, testing is not widely standardized , and there remains considerable intraindividual variability (about one-third of repeat tests conflict with initial testing ). While those with IBS do seem to have higher rates of SIBO and dysbiosis, whether this is a cause or effect of the condition remains uncertain. Above all, IBS symptoms and their intensity do not correlate with hydrogen breath testing results. Similar to IgG food sensitivity evaluation, reserve this test for those who have exhausted most other treatments, including a thorough elimination diet (FODMaP-based if IBS), and continue to have bothersome symptoms.
Newer Tests You May Not Be Familiar With
Fecal calprotectin measures inflammation, much like erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP). Unlike those two tests, it is highly specific for the gut. Elevated levels may indicate there may be inflammatory bowel disease (IBD) or another condition that would stimulate inflammation along the intestinal tract. In an individual with a high pre-test probability, this test (sensitivity in 80%-90%s) can help rule out an inflammatory bowel condition and negate the need for more invasive testing.False positives can be due to persistent nonsteroidal anti-inflammatory drug (NSAID) or proton pump inhibitor (PPI) use, or may be associated with a malignancy. Another test that can offer similar information is fecal lactoferrin; however, calprotectin is more widely available and does not require an outside lab. A normal value is <50 mcg/g.
Pancreatic elastase measures pancreatic exocrine function with very high sensitivity. It is a very useful test to rule out pancreatic insufficiency. It is rare that someone will lose their ability to make this enzyme unless he or she has a condition such as cystic fibrosis, end-stage diabetes, or chronic pancreatitis. Pancreatic elastase also can determine if taking pancreatic enzymes is necessary. If people have been using these on their own, have them stop for at least 2 weeks before checking levels. If the level normal, taking pancreatic enzymes is likely not helpful and may impede endogenous pancreatic exocrine function. A normal value is >200 mcg/g.
Impedance and pH testing
This test evaluates gastroesophageal reflux disease (GERD). It determines whether reflux symptoms are related to acid reflux or a nonacidic etiology. This information can help guide whether or not to provide long-term acid suppression, which can have adverse effects.
During the test a catheter passes through the nose with sensors that monitor acid and pressure at different levels along the esophagus. Impedance sensors measure resistance to electrical current and can correlate a reflux episode with the pH of the esophagus. This can help determine whether reflux symptoms are associated with acidity. If not, consider alternative non-acid-inhibiting therapies. For additional information, refer to the GERD Whole Health tool.
The catheter hooks to a computer. A patient documents reflux episodes, eating, and sleep to help establish patterns. The patient cannot shower for the 24 hours the monitor is in place.
Fecal immunochemical test
The fecal immunochemical test (FIT) is similar to the traditional stool guaiac test but does not require drug, supplement, or dietary restrictions. It is also less likely to be positive with bleeding from the upper GI tract, because it detects hemoglobin using an antibody. Hemoglobin gradually degrades while traveling from the upper to lower GI tract. It is less sensitive than fecal occult blood testing (60-70% vs. 90%), though it is more specific (98% vs. 91%). A 2012 study of over 52,000 subjects randomized to FIT versus colonoscopy found both to be similarly effective in detecting colon cancer. FIT was better accepted by participants, while colonoscopy detected more adenomas. We still do not know if FIT testing, alone, improves disease-specific or overall mortality.
Fecal DNA testing
A range of tests is now available, but only one has FDA-approval. These tests detect various DNA abnormalities, such as KRAS mutations, aberrant NDRG4 and BMP3 methylation, and/or B-actin, for example. They have a range of sensitivities (20%-96%) but are quite specific (76%-100%). Because of concerns regarding cost-effectiveness, limited availability, and lack of superiority as compared to other screening modalities, these tests have not been widely adopted.
Celiac vs non-celiac gluten sensitivity testing
We now know that celiac disease is different from non-celiac gluten sensitivity (NCGS). Making the accurate diagnosis is important, due to the health and nutritional consequences of each. Treating celiac disease requires complete omission of gluten, and it has more concerning long-term health consequences. NCGS is not as dangerous, and patients may be able to eat gluten in small amounts.Table 1, below, offers additional comparisons between the two.
Table 1. Celiac Disease versus non-Celiac Gluten Sensivity
|Celiac||Non-Celiac Gluten Sensitivity|
|More diarrhea||More constipation|
|Presents later in life||Presents earlier in life|
|Positive serology (tTG IgA, DGP)||Negative serology (tTG IgA, DGP)|
|Symptoms of malabsorption (weight loss, diarrhea) are more common||Symptoms of malabsorption (weight loss, diarrhea) are less common|
|Order genetic testing (HLA DQ2/DQ8) if serology is borderline with symptoms of malabsorption. If negative then likely NCGS.||Not needed if serology is negative|
|Family history||No family history|
|Other auto-immune disease||No other auto-immune disease|
|Consider endoscopy and biopsy||Endoscopy and biopsy rarely needed|