Comparison of stool antigen immunoassay and serology for screening for Helicobacter pylori infection in intellectually disabled children.

Diagnosis of active Helicobacter pylori infection in intellectually disabled (ID) children is problematic because they are unable to cooperate with performance of invasive tests. In this study, the non-invasive methods of measuring serum IgG antibody concentrations and performing stool antigen tests were used to screen for H. pylori infection in ID children. Eighty-seven children with intellectual disabilities were studied. The amount of serum IgG antibody against H. pylori was measured by the ELISA method. Stool samples were examined using an amplified IDEIA HpStAR kit. To assess categorical variables, X(2) , Fisher's exact and Kappa tests were used. The stool antigen tests showed that 93.1% of the children had H. pylori antigen and the serology test that 85.1% of children were positive for H. pylori IgG antibodies. Agreement between results of H. pylori stool antigen (HpSA) testing and IgG antibody serology was 82.8%; however, according to the kappa measure of agreement this agreement is not statistically significant (value, 0.128; P = 0.19). Discordant results were observed for 15 children (17.2%): 11 (12.6%) who were positive on HpSA test but negative by serology and 4 (4.6%) who were IgG seropositive but had negative HpSA tests. This study showed a notably higher rate of H. pylori infection in ID children than has been reported by others for non-ID children from the same geographical area. The HpSA test is a valid method for primary screening for H. pylori infection in ID children; it detects the specific antigens shed during active infections and has less cross-reactivity than serological tests that detect antibodies. HpSA is a sensitive non-invasive method for detecting infection in ID children and may serve as an accurate alternative to serology.