UTILITY OF SEROLOGY IN DETERMINING HELICOBACTER-PYLORI ERADICATION AFTER THERAPY

OBJECTIVE: To determine the usefulness of four serological tests in co nfirming cure of H pylori infection before the previously reported six -month post-treatment delay. PATIENTS AND METHODS: As part of a prospe ctive, blinded, controlled trial, in which patients with duodenal ulce rs were randomized to receive different combinations of antibiotics, s erum samples were obtained in 89 patients before treatment, as well as on several occasions after treatment. Antibody titres were determined by ELISA with Bio-Rad immunoglobulin (Ig) A, Bio-Rad IgG, Pyloriset E IA-A for IgA and Pyloriset EIA-G for IgG. Eradication was confirmed wi th antral biopsy three months after therapy. RESULTS: The percentage d rop in titre following treatment was significantly larger for the grou p of patients who were treated successfully with all four kits. Optima l cut-offs for identifying successful therapy were determined, and acc uracy improved as the interval between testing and therapy was prolong ed. Six months after therapy, the IgG test from Bio-Rad achieved 100% sensitivity and 80% specificity, and that from Pyloriset achieved 88% sensitivity and 100% specificity. At three months, however, test perfo rmance was quite good, with 90% sensitivity and 80% specificity when u sing a Pyloriset IgA titre drop of 20% or greater to predict successfu l eradication. CONCLUSION: Serology is a simple, easily available, non invasive method that exhibits good positive predictive value in the co nfirmation of successful cure of H pylori infection three or six month s after treatment.