METHODOLOGICAL ASPECTS OF SEROLOGY FOR THE DIAGNOSIS OF HELICOBACTER-PYLORI INFECTION

Purpose: To discuss methodological aspects of enzyme-linked immunosorbent assays (ELISA) for the detection of Helicobacter pylori immunoglobulin G antibodies. Results of analysis: Data from several recent studies have shown that the performance of commercial ELISA kits (sensitivity, specificity, positive and negative predictive values) using a mixture of partly or highly purified antigens is usually more accurate than those based on whole-cell antigens. The performance standards of the various assays are highly dependent on the reference diagnostic methods used for assessment. of the H. pylori infection status and on the accuracy of the cut-off values established to define seropositivity or seronegativity. These may have to be set at a different threshold level depending on the age, ethnic background and prevalence of infection in the population, or depending on the purpose for, and the consequences of, the serological diagnosis. Conclusions: Since the performance values of serological assays relate to the chosen cut-off value and to the prevalence of infection, it is strongly advisable to re-evaluate a test extensively in a local reference population before use, and to establish the optimal cut-off value by a receiver-operating characteristic curve, rather than to rely on cut-off levels determined in a different population or provided by the manufacturer.