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Background: Anti-tissue transglutaminase (tTG) antibody is being used increasingly as a diagnostic tool in the serological investigation of coeliac disease. However, positive predictive values of immunoglobulin A (IgA) anti-tTG for coeliac disease in prospective studies have been disappointing and false-positive results are reported., Objective: To assess the clinical utility of cascade testing for anti-tTG and anti-endomysium antibody (AEA)., Patients: Two unselected retrospective cohorts from routine diagnostic investigation for possible gluten sensitive enteropathy: group 1 comprised 57 cases seropositive for anti-tTG and group 2 comprised 52 cases seronegative for anti-tTG. In both groups, all cases had also undergone small-intestinal biopsy., Methods: Patients were assessed for the presence of IgA anti-tTG by enzyme-linked immunosorbent assay and for IgA AEA by immunofluorescence., Results: The positive predictive value of IgA anti-tTG for biopsy-confirmed coeliac disease was 54%. The positive predictive value of dual positivity for anti-tTG and AEA was 97%. The negative predictive value of IgA anti-tTG was 100%., Conclusions: The data presented here support the use of IgA anti-tTG as an initial screen for coeliac disease. Coeliac disease is unlikely when IgA anti-tTG is absent. However, many false-positive results are seen, and clinical utility and diagnostic efficiency are improved markedly if positive results are confirmed with the more accurate, but labour-intensive, AEA assay.

Background: Anti-tissue transglutaminase (tTG) antibody is being used increasingly as a diagnostic tool in the serological investigation of coeliac disease. However, positive predictive values of immunoglobulin A anti-tTG for coeliac disease in prospective studies have been disappointing., Objective: To determine whether anti-tTG can arise as a non-specific consequence of abnormal gut permeability., Patients: A cohort from routine investigation for possible gluten-sensitive enteropathy, with 44 cases selected based on whether permeability studies had been performed., Methods: The cohort was assessed for anti-tTG by enzyme-linked immunosorbent assay, small-bowel biopsy and C-mannitol absorbency., Results: Eighteen of the 44 patients had biopsy-proven coeliac disease and 23 showed abnormal permeability. There was poor correlation between the level of anti-tTG and gut permeability., Conclusions: These data confirm an association between anti-tTG and coeliac disease but no clear relationship with other forms of increased gut permeability.