Celiac Disease: Ten Things That Every Gastroenterologist Should Know

Amy S. Oxentenko; Joseph A. Murray


Clin Gastroenterol Hepatol. 2015;13(8):1396-1404. 

In This Article

5. How Does One Evaluate for Celiac Disease in a Patient on a Gluten-free Diet?

With increasing frequency, patients start a GFD before testing for CD.[39] With data showing that patients with diarrhea-predominant irritable bowel syndrome may benefit from a GFD[40,41] and because of the media focus on a GFD, the trend will continue. Although there is little harm beyond cost to a patient on a balanced GFD, CD may be overlooked and complications ignored.

Ideally, patients who self-initiated a GFD should be evaluated for CD. First, determine the patient's willingness to resume gluten intake for testing. In the patient who refuses to resume eating gluten, this poses a challenge. The sensitivity of serology and histology diminishes with longer duration on a GFD.[2] Although serology could be checked first,[42] a positive result is the only helpful result and indicates duodenal biopsies are needed. However, if the patient has been on a GFD for less than 1 month, begin with serology because the yield may be reasonable in this period.[3] In the patient on a prolonged GFD, HLA haplotyping can be done first. Although 30%–40% of the normal population will be positive for HLA DQ2 or DQ8,[43] the absence of permissive genes will allow 60%–70% of patients to be reassured that CD is ruled out. A gluten challenge should be discussed for those carrying HLA DQ2 or DQ8 before further testing.

In the past, a gluten challenge entailed consumption of 8–10 g gluten daily for 4 weeks.[30] However, as little as 3 g gluten daily for 2 weeks will allow 75% of patients to meet diagnostic criteria for CD.[42] For those intolerant to the gluten challenge after 2 weeks, serology and duodenal biopsies should be performed. In patients tolerating gluten ingestion after the 2-week period, the challenge should continue 6 additional weeks, with serology performed after the 8-week challenge. If serology is positive, then duodenal biopsies are done. If seronegative, repeat serology after 2–6 additional weeks because a delayed rise in serologic titers may occur.[42]

Practical Suggestion

In patients requiring an evaluation for CD while on a GFD, testing for the presence of HLA DQ2 or DQ8 identifies those requiring further testing. In patients positive for HLA DQ2 or DQ8 and not highly sensitive to gluten ingestion, testing after a low-dose (3 g daily) gluten challenge for 6 weeks may suffice to diagnose CD.