Our health editor offers six important tips for anyone preparing for celiac testing.

Testing for celiac disease involves two main steps—blood tests followed by an intestinal biopsy. However, the process isn’t always straightforward. Questions, confusion, and even misdiagnosis happen all too often. Here’s how to avoid common testing pitfalls.

1. Don’t go gluten-free before testing is complete. When you go gluten-free, celiac antibodies in the blood start to disappear and intestinal tissue begins to heal. Depending how long you’ve been gluten free—the amount of time varies person-to-person—testing will come back inconclusive or normal, even if you have celiac disease.

2. Be sure a “Total Serum IgA” test is part of your blood work. Celiac blood tests fall short in up to 10 percent of people with celiac disease. Often this is due to a harmless condition called IgA deficiency, where the body doesn’t make enough of the IgA antibody for IgA-based celiac tests to be accurate. If you’re low on IgA, other blood tests can be used to help determine whether you have celiac disease.

3. A biopsy should always be taken during endoscopy. Surprisingly, not all doctors take a biopsy sample during the endoscopy procedure. At least four biopsy samples (of the duodenum and bulb) should be taken since damage due to celiac disease can be patchy—and easily missed. And in case you’re wondering, experts still recommend the biopsy to confirm celiac disease in children as well as adults since blood tests aren’t perfect.

4. A positive genetic test doesn’t mean you have celiac disease. The genetic markers for celiac disease—DQ2 and DQ8—are present in up to 40 percent of the population, yet only 1 percent has celiac disease. The genetic test can only tell you that you don’t have celiac disease.

5. Don’t rely on unproven tests. Direct-to-consumer tests such as stool kits or saliva tests aren’t proven, validated, or FDA-approved.

6. Don’t assume you’re in the clear if you’ve been tested once. Research has shown celiac disease can develop at any age, even in one’s 80s or 90s. If you’re at risk for celiac disease because of a family history or related autoimmune disorder, repeat blood testing at regular intervals while eating a gluten-containing diet. 

Christine Boyd is Gluten Free & More‘s health editor and senior medical correspondent. Based in Baltimore, she writes frequently in print and online about the gluten-free lifestyle and has covered such subjects as gluten’s role in migraines, anxiety, infertility, and thyroid conditions, among many other topics.