Scandinavian Journal of Gastroenterology 2005; 40: 1240-3.
Dickey W, Hughes DF, McMillan SA.
Celiac.com 09/27/2005 - What does a positive endomysial antibody (EmA) test mean if the biopsy does not show villous atrophy? The authors studied 35 patients where this was the case. In the authors practice, these patients account for 10% of all EmA positives.
Firstly, the lack of villous atrophy did not necessarily mean a normal biopsy: 14 patients had excess inflammatory cells (lymphocytes) consistent with a mild abnormality of gluten sensitivity.
Secondly, many of these patients had typical celiac features: twelve had a family history of celiac, five had dermatitis herpetiformis and thirteen had osteopenia or osteoporosis on DEXA scan.
After discussion, 27 patients opted to take a gluten-free diet from the first biopsy: 26 of these had clinical improvement. Seven of eight patients who persisted with a normal diet developed villous atrophy on follow-up biopsies.
The authors conclude that a positive EmA result indicates gluten sensitivity even if biopsies do not show villous atrophy. While a biopsy remains important as a baseline reference, these patients should be offered a gluten-free diet to allow clinical improvement and prevent the development of villous atrophy. There may be no such thing as a "false positive" EmA, although the authors emphasise that the same conclusion cannot yet be applied to tissue transglutaminase antibody results.