Determinants of endomysial antibody status in untreated coeliac disease.

Background: Serum endomysial antibody (EMA) is a highly specific marker of untreated coeliac disease (CD). The published estimates of sensitivity however vary widely and the explanation for this remains unclear.

Objective: To determine the relative prevalence of EMA-negative CD and to identify clinical and histological characteristics which relate to EMA status.

Method: Retrospective analysis of prospectively collected data on incident cases of CD in a single hospital over a 10-year period with determination of EMA status before gluten withdrawal.

Results: From a total of 241 participants, 37 [15% (95% confidence interval: 11, 20%)] were EMA negative, of whom only four were IgA deficient. EMA-positive and EMA-negative patients shared a number of characteristics including female predominance and a high prevalence of HLA DQ2. EMA status was associated with age-test sensitivity and exceeded 98% below the age of 35 years, falling to around 80% in older age groups overall, and lower still in current cigarette smokers. EMA status was not influenced by sex, family history of CD, other autoimmune disease, or by potential clinical or histological markers of disease severity.

Conclusion: A substantial proportion of patients with true CD are EMA negative. This has implications for the pathogenesis of the disease. It also limits the value of EMA as a screening test, particularly in older adults and cigarette smokers.