The Re-evaluation of the Serologic ELISA tests for the Diagnosis of Helicobacter pylori Infection

Kim, Sinkyung; Kim, Think You

Abstract

BACKGROUND: Helicobacter pylori (H. pylori), a Gram negative spiral bacilli, is known to be the cause of chronic gastritis and peptic ulcer disease and is strongly associated with gastric cancer. Therefore, the rapid detection of H. pylori infection is necessary for prevention and treatment. Of the diagnostic tests currently used, the serologic tests, which makes use of the immune response, do not need a biopsy specimen. This method is relatively accurate, rapid, simple and inexpensive. We re-evaluated the clinical usefulness of the isotypes of H. pylori (IgG, IgA, IgM) antibodies for the detection of H. pylori infection.
MATERIALS AND METHODS
Serum samples were obtained from 1,851 patients confirmed to have gastric or duodenal disease by gastric endoscopy from June, 1993 to December, 1994 at Hanyang University Hospital. The phenol-red urease test was done during endoscopy and the H-E stain on the gastric biopsies. Serologic tests (GAP Test IgG, IgA, IgM kits) were performed with patient sera.
RESULTS
The sensitivities of the GAP EIA were 80% for IgG, 27% for IgA, and 85% for IgM. The specificities were 33%, 79%, and 14%, respectively. The detection rates of H. pylori were highest for the phenol-red urease test (88%), followed by IgM by ELISA (86%), IgG (72%), H-E stain (43%), and IgA (21%). The serum levels of IgG and IgA antibodies were higher in those with H. pylori infection than in those without, but there was no difference in IgM levels. And, no difference of serologic antibody levels according to disease state. Where follow-up was possible, the majority of IgG levels decreased, but IgA or IgM levels are not changed.
CONCLUSION
A positive serologic test is incapable of discriminating between actual infection and normal bacterial colonization, or between recent and past infections. Therefore a serologic test seems unsatisfactory for confirming a diagnosis of H. pylori infection, but because the serial IgG levels of treated patients decreased significantly, we believe that this test may be used as an indirect means of assessing the response to therapy.