Tissue transglutaminase immunoglobulin A exceeds endomysial antibody in specificity of celiac diagnosis at ≥10 times the upper limit of normal.

Objective: Serologic diagnosis using tissue transglutaminase immunoglobulin A (TTG-IgA) and endomysial antibody (EMA) is being integrated into the care of pediatric patients with positive screening for celiac disease. The purpose of this study was to assess the utility of EMA in pediatric patients being considered for serologic diagnosis.

Methods: Patients with TTG-IgA testing performed between May 1, 2022 and April 30, 2023 and with subsequent duodenal biopsy within 6 months were included. TTG-IgA serum samples were frozen and sent for EMA testing and titer. EMA was evaluated for positivity and TTG-IgA (normal <15 u/mL) for elevation <10 times (10x) the upper limit of normal (ULN) and ≥10x ULN (≥150 u/mL). Sensitivity and specificity of EMA and TTG-IgA were calculated using biopsy histology as the gold standard.

Results: Four hundred and eighty-six patients were included. The sensitivity and specificity of TTG-IgA ≥15 u/mL was 87.5% and 95.4% while EMA was 77.5% and 97.3%. For patients with TTG-IgA ≥10x ULN the specificity was 99.3%. The positive predictive value of TTG-IgA at ≥10x ULN was 91.4% and for EMA was 83.6%. All three patients with false positive TTG-IgA ≥10x ULN also had false positive EMA, and two of these patients had type 1 diabetes mellitus.

Conclusions: TTG-IgA has greater sensitivity at the screening threshold of ≥15 u/mL and greater specificity and positive predictive value at ≥10x ULN than EMA. TTG-IgA at ≥10x ULN is superior to EMA for the serologic diagnosis of celiac disease.