Specialty Testing Guide › GI-MAP Gut Testing
Besides microbes, a GI-MAP reports a set of "intestinal health markers": proteins and antibodies in stool that hint at digestion, gut immunity, inflammation and bleeding. They include secretory IgA, elastase, steatocrit, beta-glucuronidase, anti-gliadin IgA, an eosinophil protein, occult blood and calprotectin, with zonulin available as an add-on.
These markers are not equally reliable. Elastase and calprotectin are used in mainstream gastroenterology and have guideline support. Others, including secretory IgA and beta-glucuronidase, have limited evidence for guiding care, and stool zonulin rests on assays with documented problems. Knowing which is which keeps you from over-reading your report.
Key takeaways
- Elastase and calprotectin are the most clinically established markers on the report, and abnormal results deserve standard follow-up.
- Secretory IgA reflects antibody activity in the gut, but there is limited evidence that a single stool value should change treatment.
- Beta-glucuronidase and zonulin are research-level markers, and commercial zonulin tests may not measure zonulin at all.
- Anti-gliadin IgA in stool cannot diagnose or rule out celiac disease, which needs blood tests and usually a biopsy.
Secretory IgA: the gut's front-line antibody
IgA is the primary antibody in the gut lining. Secretory IgA coats the inner surface of the bowel and helps keep microbes and food proteins in check. The gut carries a large share of the body's antibody-producing cells: one review estimated that about 80% of plasma cells, mainly IgA-bearing cells, reside in gut-associated lymphoid tissue.1
The GI-MAP sample report gives a reference range of 510 to 2010 micrograms per gram for secretory IgA.2 The lab reads a low value as a suppressed gut immune response and a high value as an active response to infection, dysbiosis, stress or foods.3
Those readings are plausible, but stool secretory IgA is not a routine test in standard gut care, and its level shifts with many everyday factors. Treat a mildly high or low result as a clue to read alongside your symptoms and other findings, not as a diagnosis or a reason for long supplement lists.
Elastase and steatocrit: digestion markers
Pancreatic elastase-1 is an enzyme made only by the pancreas, so a low stool level can point to exocrine pancreatic insufficiency (EPI), where the pancreas does not release enough digestive enzymes.
The American Gastroenterological Association calls fecal elastase the most appropriate first test for EPI and says it must be done on a semi-solid or solid stool.4 Under that guidance, a level below 100 micrograms per gram provides good evidence of EPI, and 100 to 200 is indeterminate.4
The GI-MAP interpretive guide labels results of 200 to 500 as "decreased pancreatic output."3 That label is the lab's own and is not an EPI diagnosis. Watery stool can also dilute the result, so a low number from a loose sample should be interpreted with care.
Steatocrit estimates fat in the stool. High fecal fat can reflect poor digestion or absorption from pancreatic, gallbladder or small bowel problems, including celiac disease. The same AGA update notes that formal fecal fat testing is rarely needed and must be done on a high-fat diet, so a single steatocrit on a mixed diet is a rough screen at best.4
Beta-glucuronidase
Beta-glucuronidase is an enzyme made by some gut bacteria. It can undo a step the liver uses to package hormones and other compounds for removal, which is why it is discussed in relation to estrogen recycling. The lab's guide links high levels to dysbiosis and to problems clearing estrogen and other compounds.
Those ideas are biologically plausible. Still, beta-glucuronidase is not used in standard gastroenterology care, and there is limited evidence that lowering a stool level improves hormone-related symptoms. Treat it as a research-level marker.
Anti-gliadin IgA, eosinophil protein and occult blood
Anti-gliadin IgA measures an antibody response to a part of gluten inside the gut. The lab's own guide notes that fecal anti-gliadin antibodies do not necessarily correlate with blood levels.3 Celiac disease is diagnosed with blood antibody tests followed in most patients by a biopsy, not a stool antibody.5 See celiac disease testing guidelines before changing your diet.
Eosinophil activation protein reflects activity of eosinophils, white cells involved in allergy and some infections. A high value is nonspecific and is best read alongside your history of allergies, reflux and gut symptoms.
Occult blood uses an antibody test for human hemoglobin. A positive result needs medical follow-up to find the source, whatever the rest of the report shows. It is not a substitute for routine colorectal cancer screening.
Zonulin: an add-on with assay problems
Zonulin is promoted as a marker of "leaky gut," and the lab offers it as an optional add-on, so ask our team whether it is part of the panel ordered for you. The concern is the measurement itself. An independent study found that widely used commercial zonulin assays were not detecting the actual zonulin protein and advised caution in using them as a marker of gut barrier integrity.6
That study looked at blood tests, but stool zonulin relies on the same kind of antibody kit, so the same caution is reasonable. Our article on zonulin and intestinal permeability tests covers the details.
How solid is each marker, and what comes next
| Marker | What it may suggest | Strength of evidence |
|---|---|---|
| Calprotectin | Bowel inflammation | Well validated for IBD vs IBS triage |
| Elastase-1 | Low pancreatic enzyme output | Established first test for EPI |
| Occult blood | Bleeding somewhere in the gut | Established; positive needs follow-up |
| Steatocrit | Fat maldigestion or malabsorption | Rough screen only |
| Secretory IgA | Gut immune activity | Limited evidence for guiding care |
| Eosinophil protein | Allergy-type or eosinophilic inflammation | Nonspecific |
| Anti-gliadin IgA (stool) | Gut immune response to gluten | Not validated for celiac diagnosis |
| Beta-glucuronidase | Bacterial enzyme activity | Research-level |
| Zonulin (add-on) | Claimed barrier permeability | Documented assay problems |
For the best-studied marker, see calprotectin explained.
Abnormal established markers, such as low elastase, high calprotectin or a positive occult blood, lead to standard medical follow-up first. Softer markers are context. Our article on after your GI-MAP results explains how a results visit works, in person in Conshohocken or by telehealth within Pennsylvania, and the GI-MAP hub lists the rest of the guide.
Frequently asked questions
My secretory IgA is low. Is my immune system weak?
Not necessarily. Stool secretory IgA varies with diet, stress, infection and sampling, and a single value says little about overall immunity. Read it alongside your symptoms and other results.
My elastase is between 200 and 500. Do I need enzymes?
The lab labels that range as decreased output, but AGA guidance treats only values below 200 as indeterminate or suggestive of exocrine pancreatic insufficiency. Discuss symptoms such as oily stools or weight loss with your clinician before starting enzymes.
Does a high zonulin prove I have leaky gut?
No. The assays used to measure zonulin have documented accuracy problems, and there is no validated test result that diagnoses "leaky gut" as a condition.
Related reading
This article is for general education and is not medical advice. Decisions about testing and treatment should be made with your clinician. If you have severe symptoms, call 911. For a suspected poisoning, call Poison Control at 1-800-222-1222.
