A 31-year-old woman had intermittent abdominal cramping for years; the cramping has improved with a gluten-free diet. The patient has been following this diet for about 1 year. She is now inquiring whether she has celiac disease. Which of the following tests should be ordered next to rule out celiac disease?
A. Tissue transglutaminase (tTG)
B. Duodenal biopsies
C. Human leukocyte antigen DQ2/DQ8
D. Capsule endoscopy
Correct answer: C
Improvement of symptoms with a gluten-free diet does not necessarily equate to a diagnosis of celiac disease. Many patients with gluten sensitivity or with conditions such as diarrhea-predominant irritable bowel syndrome may note clinical improvement with a gluten-free diet. The optimal test used for primary detection of celiac disease is an IgA anti-tissue transglutaminase test. The sensitivity of tTG-IgA in untreated celiac disease is about 95%; however, patients on a strict gluten-free diet for several months may no longer demonstrate antibodies. For similar reasons, duodenal biopsies may no longer demonstrate histologic features of celiac disease. Options for this patient are to rechallenge herself with gluten, then perform serologic testing for screening. However, many patients may be reluctant to do this. Therefore, an HLA DQ2/DQ8 can be checked. This has excellent negative predictive value and would be useful in ruling out celiac disease. Capsule endoscopy is not necessary for diagnosis; however, this is an alternative method to endoscopy for confirming villous atrophy.