Radioimmunological detection of anti-transglutaminase autoantibodies in human saliva: a useful test to monitor coeliac disease follow-up

Background Serum radioimmunoassay (RIA) tissue transglutaminase autoantibodies (tTG-Abs) proved to be a sensitive test also during coeliac disease (CD) follow-up. We demonstrated that RIA tTG-Abs could be detected in human saliva. Aim To evaluate salivary RIA tTG-Abs in coeliac children on gluten-free diet (GFD). Methods Saliva and serum samples from 109 coeliac children were evaluated at diagnosis (group 1: 71 females, median age 9.4 years) and 58 of them on GFD: 36 after 3-6 months (group 2a), 34 at 9 months or more (group 2b). Two gender- and age-matched control groups: 89 gastroenterological patients (group 3) and 49 healthy subjects (group 4) participated in the study. Saliva and serum tTG-Abs were detected by RIA and compared with serum tTG-Abs ELISA and IgA anti-endomysium antibodies (EMA). Results Salivary RIA tTG-Abs were found in 94.5%, 66.7% and 50.0% of groups 1, 2a and 2b CD patients and in 98.2%, 72.2% and 50.0% of corresponding serum samples, respectively. tTG-Abs decreased with GFD progression and a correlation was found between saliva and serum titres (r = 0.75, P = 0.0001). During the CD follow-up, salivary and serum RIA sensitivities were comparable, and higher with respect to EMA and ELISA. Conclusions This study demonstrates that it is possible to detect salivary tTG-Abs with high sensitivity not only at CD diagnosis, but also during GFD.