Helicobacter pylori seroconversion in asymptomatic blood donors - A five-year follow-up

Several techniques have been developed to diagnose Helicobacter pylori infe ction and two noninvasive methods are available: carbon 13-urea breath test (UBT) and serology. Measurement of IgG serum antibodies by enzyme-linked i mmunosorbent assay (ELISA) is a reliable and inexpensive method for detecti on of infection. The aim of this study was to assess the seroconversion by different techniques after five to eight years. In 1990, 588 of 1010 asympt omatic donors were found to be seronegative by ELISA, based on an N. pylori whole-cell suspension lysate (sensitivity and specificity: 92% and 97%). I n 1995 serum samples from 418 of 588 seronegative donors were collected and retested using the same antigen. 411 of 418 samples were frankly negative, and 7 donors were found to be seroconverted. This group of seven sera repr esents the object of the study. They were retested by ELISA and western blo tting using a different antigen (NCTC). To standardize our techniques, sera from 43 H. pylori positive and 47 H. pylori negative patients according to culture, histology, urease test, and UBT were used. The cutoff for ELISA-N CTC was 0.53 AI (absorbance index) (mean value + 2 SD), and for western blo tting was negativity for CagA or <10 bands (sensitivity and specificity: 95 % and 96%; 98% and 81% for ELISA and western blotting respectively). Accord ing to the results obtained in 1990 and 1995, seven donors were found to be seroconverted by ELISA using sonicated antigen; in five the seroconversion was confirmed by ELISA using NCTC antigen and in two there was concordance with WB. Four of the seven donors were contacted and asked to undergo UBT and a further serum sample was drawn to be reassessed in 1998. A seroconver sion was found in all four donors by ELISA while WB and UBT confirmed the s eroconversion in only three of four donors. In conclusion the in-house ELIS A used performed well compared to other theoretically better serologic assa ys and confirmed the low seroconversion rate for N. pylori infection in adu lt populations living in developed countries.