Western blotting is useful in the salivary diagnosis of Helicobacter pylori infection

Background-The salivary diagnosis of Helicobacter pylori infection offers a ttractive possibilities for the epidemiological study of infection in child ren. Salivary enzyme linked immunosorbent assay (ELISA) is less reliable th en serum ELISA, owing to variable transudation of immunoglobulin. In additi on, children are more difficult to study because of lower specific serum an tibody concentrations to H pylori. The performance of salivary western blot ting in comparison with serum western blotting and serum ELISA was investig ated in school children. Subjects and methods-Paired serum and saliva specimens were obtained from 6 55 school children aged 9-11 in 10 British towns. All saliva and serum spec imens were first analysed by ELISA; subsequently, western blotting of both specimens was performed on 31 and 34 specimens, respectively, to establish the criteria for positivity for western blotting. The remaining 121 specime ns were then tested blindly and saliva was compared with the serum. Results-The sensitivity and specificity of salivary ELISA in the 665 specim ens was 32 of 50 (64%) and 530 of 691 (87%), respectively, when compared wi th serum ELISA. The western blotting validation was performed on 28 subject s with positive serum and positive salivary ELISA, 28 saliva positives with negative serum, 16 saliva negatives with positive serum, and 50 doubly neg ative subjects. Compared with serum western blots, the sensitivity and spec ificity of salivary western blots was 38 of 47 (81%) and 68 of 75 (91%), re spectively. Using serum ELISA as the gold standard, the sensitivity and spe cificity were 32 of 44 (73%) and 72 of 78 (92%), respectively, the specific ity being significantly higher than salivary ELISA (p < 0.001). Conclusion-Salivary western blotting for IgG is useful in the diagnosis of H pylori infection and is superior to ELISA. It also permits the identifica tion of pathogenic strains.