Serum IgG antibody tests for Helicobacter pylori remain positive months after treatment. Currently, paired serologies can be used to determine cure, or a patient can undergo urea breath tests or gastric biopsy. If symptoms recur, even a year later, the physician is left wondering if the patient has persistent or recurrent disease. Feldman and colleagues conducted a prospective study to determine the role of serologic testing in confirming cure of H. pylori infection more than one year after treatment.

Ten men and 13 women were included in this study; none had a history of peptic ulcer disease or chronic upper gastrointestinal tract symptoms. At baseline, H. pylori serum antibody tests were positive in each patient, as were gastric biopsies. Each patient was then treated with a two-week course of 524 mg of bismuth subsalicylate four times daily, 500 mg of tetracycline four times daily and 250 mg of metronidazole four times daily. Serum antibodies were retested, and mucosal biopsies of the gastric body were performed one, three and 18 months after completion of therapy. Biopsies of the gastric antrum were performed at three and 18 months. Cure was defined as absence of H. pylori organisms on both gastric biopsies at 18 months. Persistence was defined as the presence of organisms on biopsy specimens 18 months after therapy.

H. pylori infection was cured in 65 percent of the patients in the study approximately 18 months after antimicrobial therapy. In the remaining eight patients, infection persisted. Even in these patients, there was a 50 percent decrease in gastritis severity score at one month, but this was followed by an increase in severity over subsequent months. In the eight patients with persistent infection, H. pylori serum antibody levels did not change significantly over the course of the study. H. pylori seroconversion from positive to undetectable serum antibody levels at 18 months had a sensitivity of 60 percent for diagnosing cure of H. pylori infection and a specificity of 100 percent.

The authors conclude that a patient who was treated for H. pylori infection more than one year previously can reliably be considered cured if serum H. pylori antibody levels change from positive (pre-therapy) to negative. This serum test should probably be the test of first choice, since a negative test result would preclude the need for a urea breath test or gastric biopsy in most patients. If the patient has not seroconverted, the test result should be considered nonspecific, and a urea breath test or gastric biopsy should be done to confirm either cure or persistent infection. A serology test remains insensitive for confirmation of cure during the first three months after treatment.