Significance of Transiently Positive Enzyme-Linked Immunosorbent Assay Results in Detection of Helicobacter pylori in Stool Samples from Children

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Abstract
In young children, the significance of stool samples transiently positive for Helicobacter pylori antigen is unknown. As part of a larger prospective study on enteric infections, stool samples were obtained from 323 children at two time points 3 months apart and tested for H. pylori antigen using a commercially available enzyme-linked immunosorbent assay (ELISA) test. Seminested PCR for a Helicobacter -specific 16S rRNA gene was performed on all 26 pairs reverting from positive to negative (transient positives), all 4 persistent antigen-positive pairs, and 10 randomly selected persistent antigen-negative pairs. Helicobacter species were amplified from the first stool samples of 15/26 (58%) of the transient positives and 1 (25%) of 4 persistent positives. No Helicobacter species were amplified from the 10 persistent negatives. Among the 15 amplicons from transient-positive stool, H. pylori was sequenced and identified from 12 (80%; 95% confidence interval, 52% to 96%) and other Helicobacter spp. were identified from three ( Helicobacter canis , Helicobacter winghamensis , and MIT 99-5504). Four of the 15 remained positive by PCR for the second (antigen-negative) stool sample, including all 3 initially identified as non- H. pylori. Helicobacter bilis was amplified from the second sample of a persistent positive. Two of eight transient positives from whom serum was available had accompanying transient elevations in anti- H. pylori antibodies. Transiently positive stool ELISAs for H. pylori are common and represent H. pylori in the majority of cases where sequences can be obtained. A not-insignificant percentage of antigen-positive stools, however, may represent other Helicobacter species.