Comparison of PCR and clinical laboratory tests for diagnosing H. pylori infection in pediatric patients

Kathleen Mb Vinette,Kathleen M Gibney,Roy Proujansky,Paul T Fawcett

doi:10.1186/1471-2180-4-5

Abstract

BackgroundHistology and/or culture are generally considered the gold standard for the detection of H. pylori infection. Especially in children, these tests may result in a false negative outcome because of patchy distribution of the organism in the stomach mucosa. We have developed a PCR assay utilizing nested primer pairs directed against a subunit of the H. pylori urease gene (ureA). As part of a prospective evaluation of diagnostic tests to aid in detecting H. pylori infection in children, the aim of this study was to compare our PCR and Western blot assays with results obtained from histologic examination of biopsy specimens, rapid urease tests, and an FDA approved serologic assay and published PCR results to determine if we could validate the assays for diagnostic use on our patient population.ResultsGastric biopsy specimens obtained from 101 pediatric patients were evaluated for the presence of H. pylori using histologic techniques, rapid urease (CLOtest) test and the PCR assay. Serum samples from each patient were assayed using both ELISA and Western Blot for antibodies to H. pylori. A total of 32 patients tested were positive by at least one of the methods evaluated. Thirteen patients had positive histology, 13 had a positive CLOtest, and 17 patients had positive H. pylori PCR. Out of the 13 CLO positive patients, 12 were positive by histologic analysis and all 13 were positive by PCR. Results of serologic tests on the same population did not correlate well with other assays. Twenty-eight patients showed serologic evidence of H. pylori infection, of which 9 were both CLO and histology positive and 12 were positive by PCR. Of the seropositive patients, 26 were ELISA positive, 13 were positive by Western blot, and 11 by both serologic methods.ConclusionsThe results obtained suggest that our nested PCR assay has the specificity and sensitivity necessary for clinical application when compared to standard histologic examination and rapid urease test. In addition, we found the current commercially available approved ELISA method appears unable to accurately detect H. pylori in this population. The Western blot assay yielded better concordance with CLOtest and histology, but not as good as the nested PCR assay.

Highlights

Histology and/or culture are generally considered the gold standard for the detection of H. pylori infection
Patient samples were considered to be positive for H. pylori by Polymerase chain reaction (PCR) amplification if the 279 bp band was seen in the initial reaction and/or the 120 bp was seen in the internal nested reaction
◆ Results of the nested PCR assay for detection of the Helicobacter pylori urease A gene in pediatric gastric biopsies show good correlation with results obtained from CLOtest slides and histologic examination

Summary

Introduction

Histology and/or culture are generally considered the gold standard for the detection of H. pylori infection. In children, these tests may result in a false negative outcome because of patchy distribution of the organism in the stomach mucosa. With biopsy of the affected region followed by histologic examination of stained specimens to demonstrate the presence of the bacterium and culture of the bacterium from the tissue. Not routinely performed, is considered the gold standard for the diagnosis of H. pylori infection. Biopsy specimens are used to detect the presence of the H. pylori urease This biopsy urease test (Campylobacter-like organism or CLOtest) is considered rapid and economical, and is in widespread use in clinical practice. A rapid EIA to detect H. pylori antigen in stool has become available [7]

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