Serum 13C-bicarbonate assay for the diagnosis of gastric Helicobacter pylori infection and response to treatment.

Abstract

Current serological tests for Helicobacter pylori (HP) infection are not useful in assessing active infection or eradication. The feasibility, sensitivity, and specificity of serum 13C-bicarbonate (13C-HCO3) measurement in determining gastric HP before and after eradication by antibiotics were investigated. Twenty-seven symptomatic patients underwent endoscopy, biopsy, and CLOtest. Patients then consumed a 13C-urea-rich meal; serum was collected before and 1 hour after meal ingestion for quantitative determination of 13C by mass spectrometry. Postprandial fractional elevation of 13C (delta 13C-HCO3) was correlated with endoscopy, histology, and CLOtest at baseline and at 4 and 8 weeks after therapy. delta 13C-HCO3 +/- SEM was 17.02 +/- 2.94 in HP-positive patients and 2.77 +/- 044 in HP-negative patients (P < 0.0001). In HP-positive patients who responded to therapy, the mean change was initially 20.5 +/- 3.1, 3.2 +/- 0.9 1 month after therapy, and 2.8 +/- 0.4 2 months after therapy (P < 0.001). The overall sensitivity of this method was 90.6% (95% confidence interval, 74.9-98.0), and its specificity was 85.7% (95% confidence interval, 42.1%-99.6%). delta 13C-HCO3 correlated positively with the degree of histological gastritis and the number of HP organisms. Serum 13C-HCO3 analysis is a novel, simple, and noninvasive method for diagnosis and assessment of eradication of HP infection.