Antibodies against human tissue transglutaminase and endomysium in diagnosing and monitoring coeliac disease

BACKGROUND: Coeliac disease (CD) patients often present a variety of uncharacteristic symptoms and therefore sensitive and specific screening tests are needed as an aid in making an accurate diagnosis. A recently developed ELISA, using human recombinant tissue transglutaminase (tTG) as antigen, was evaluated for its significance in the diagnosis of CD. The patient's compliance to a gluten-free diet and the serological reaction during gluten challenge were also monitored. The results were compared with IgA-endomysium antibody (EMA) results. METHODS: Sera previously collected from 365 patients (0.4-76 years) with jejunal biopsy on a gluten-containing diet and from 41 patients on a gluten-free diet or challenge were tested for IgA anti-human tTG antibodies (IgA tTG ab) with Celikey (Pharmacia Diagnostics). The study population comprised 208 CD patients and 157 controls. The diagnostic performance and cut-off for the assay were estimated with ROC analysis. EMA was analysed by indirect immunofluorescence microscopy on cryostat sections of monkey oesophagus. RESULTS: 200/208 patients with CD had positive IgA tTG ab (median >100 U/ml), while only 1/157 of the control patients were positive (median 1.67 U/ml). The area under the ROC curve was 98.3% and the sensitivity and specificity of the test were 96% and 99% for the study population. Only 4/365 patients (1%) presented discordant IgA tTG ab and EMA results, 2 of them had only IgA tTG ab and 2 only EMA. The IgA tTG ab levels and the EMA titres were closely correlated to the duration of gluten-free diet and gluten challenge, respectively. CONCLUSION: IgA tTG ab can be used as an accurate observer-independent alternative to EMA in diagnosing or monitoring CD.