Characteristics of differences in Helicobacter pylori serology and C-13-urea breath-testing in an asymptomatic sample of blood donors

Numerous tests, both invasive and non-invasive, are available for the diagn osis of Helicobacter pylori infection. The aim of this study was to evaluat e the extent and determinants of differences in serology and C-13-urea brea th test (C-13-UBT) in diagnosing H. pylori. Four-hundred-and-seventy-four a symptomatic blood donors aged 40 to 68 years (mean age 55.8 years) and of G erman nationality were recruited between October 1996 and November 1997. H. pylori infection was measured with C-13-UBT and with a commercial IgG-ELIS A test (Medac; Hamburg. Germany). A standardized questionnaire was applied to identify factors which could explain discrepant results of C-13-UBT and serology. Prevalence of infection was similar according to both tests (33.1 % for C-13-UBT and 30.8% for serology). From the 146 subjects with a positi ve serology, 121 (82.7%) had a positive C-13-UBT. Previous treatment of H. pylori infection was the strongest predictor of a negative C-13-UBT given p ositive IgG serology (odds ratio (OR) = 12.87, 95% CI = 4.10-40.36). Coffee consumption of more than 3 cups/day was also associated with an increased odds of a negative C-13-UBT given positive serology (OR = 3.12, 95% CI = 1. 16-8.43). No significant determinants of positive C-13-UBT given negative s erology could be identified. These findings suggest a delayed fall in serum antibodies following eradication of the infection to be a major source of differences in H. pylori diagnosis using non invasive C-13-UBT and serology .