Role of human-tissue transglutaminase IgG and anti-gliadin IgG antibodies in the diagnosis of coeliac disease in patients with selective immunoglobulin A deficiency.

Background: Selective IgA deficiency is associated with coeliac disease, and studies have shown an increased prevalence of coeliac disease in these patients ranging from 0.71 to 30.7%, depending on the test used for screening.

Aims: To determine the sensitivity of IgG anti-gliadin-antibodies and of IgG human-tissue-transglutaminase for diagnosing coeliac disease and assessing its prevalence in subjects with IgA deficiency.

Subjects: We tested serum samples from 126 IgA-deficient children (66 female, median age: 10.8 years).

Methods: All samples were analysed to measure IgG anti-gliadin-antibodies and IgG anti-human-tissue-transglutaminase. Patients testing positive to either test underwent intestinal biopsy. Subjects testing positive for IgG anti-human-tissue-transglutaminase underwent genetic testing for the human leucocyte antigen heterodimer.

Results: Twenty-seven of 126 subjects tested positive for IgG anti-gliadin-antibodies (five of whom tested positive also for IgG anti-human-tissue-transglutaminase) and 18 (including the aforementioned five) for IgG anti-human-tissue-transglutaminase. Intestinal biopsy was performed in 37 of the 40 patients who tested positive (three subjects refused). Eleven had positive intestinal biopsies all of whom tested positive for IgG anti-human-tissue-transglutaminase, but only five of these tested positive also for IgG anti-gliadin-antibodies. All 22 patients testing positive for anti-gliadin-antibody alone had normal intestinal mucosa. All the patients who tested positive for IgG anti-human-tissue-transglutaminase and underwent genetic screening (15/18) had the coeliac-related human leucocyte antigen. Overall, coeliac disease was diagnosed in 11 of the 126 subjects with IgA deficiency (8.7%).

Conclusions: The prevalence of coeliac disease in subjects with total IgA deficiency was 8.7%. Assay of IgG anti-human-tissue-transglutaminase can be recommended for screening coeliac disease in IgA-deficient subjects.