Kinetics of specific IgG antibodies for monitoring the effect of anti-Helicobacter pylori chemotherapy.

A total of 104 patients with recurrent duodenal ulcer were treated with either ranitidine plus amoxicillin plus metronidazole or ranitidine plus placebo. To study the effect of the eradication of Helicobacter pylori on the systemic immune response in an IgG ELISA, sera were drawn from all patients before the onset of therapy and at 6, 16 +/- 2, 32 +/- 2, and 60 +/- 2 weeks after therapy. In patients with eradication of the organism, a significant (P < .001) reduction of the specific IgG titer occurred. This was not observed in patients without bacterial eradication. If a titer reduction of > 50% was taken as an indicator for eradication of H. pylori, the sensitivity of the serologic test was 97.6%-99.7%. Its specificity increased with the interval to the onset of chemotherapy from 56.3% to 97.6%. Serologic tests are simple to perform and cause very little discomfort to the patient.