Detection of secretory IgA antibodies against gliadin and human tissue transglutaminase in stool to screen for coeliac disease in children: validation study

Objective To evaluate two commercial stool tests for detection of
secretory IgA antibodies against gliadin and human tissue
transglutaminase for diagnosis of coeliac disease in children with
symptoms.Setting Tertiary care children's hospital.Participants
Coded stool samples from 20 children with newly diagnosed coeliac
disease and 64 controls. Six children with coeliac disease had
stool tests every two weeks for three months after starting a
gluten-free diet.Main outcome measures Secretory IgA antibodies
against gliadin and human tissue transglutaminase in stool samples,
determined in duplicate by using recommended cut-off limits.Results
Sensitivity of faecal antibodies against human tissue
transglutaminase was 10% (95% confidence interval 1% to 32%), and
specificity was 98% (91% to 100%). For antibodies against gliadin,
sensitivity was 6% (0% to 29%) and specificity was 97% (89% to
100%). Optimisation of cut-off limits by receiver operating
characteristic analysis and use of results of both tests increased
sensitivity to 82%, but specificity decreased to 58%. All follow-up
stool tests remained negative, except for two positive anti-gliadin
results in one patient, six and 10 weeks after the gluten-free diet
was started.Conclusions Neither stool test was suitable for
screening for coeliac disease in children with symptoms.