Use of the 'Polymerase Chain Reaction' for the diagnosis of Helicobacter pylori infection

PURPOSE: H. pylori infection can be diagnosed by means of non-invasive tests or invasive techniques using endoscopy. The choice of the test depends on available instruments, type of diseases, aim of diagnostic research (therapeutic or epidemiological) and test features. PCR is able to reveal pathogenic germs in biological material with very high sensitivity and specificity. In vitro DNA amplification method consists of hybriding denaturated DNA by means of two oligonucleotide primers that allow to copy DNA fragment. The aim of our study was to determine, using PER, H. pylori colonization in the gastric mucosa of 18 consecutive patients under-went gastroscopy. MATERIALS AND METHODS: Eighteen patients complaining of dyspeptic symptoms and referred to us for upper GI endoscopy participated in the study. The studied population comprised 9 males and 9 females with mean age of 55.4 yrs (range 26-73 years). All patients underwent gastroscopy during which 4 biopsies from the antrum and 4 from the corpus were obtained for Giemsa stain, PCR analysis and histologic examination. A pair of synthetic oligonucleotides for H. pylori urease A gene, designated as HPU1 and HPU2, were used. Urease A gene fragment amplified by PCR was analyzed by 1.5 agarose gel electrophoresis. Positivity for H. pylory corresponded to PCR DNA products migrating at 411 bp after staining with ethidium bromide. RESULTS: The patients were divided into two groups, according to H. pylori infection, determined by means of Giemsa stain: group A, comprising 11 H. pylori-positive patients; and group B, with 7 H. pylori-negative patients. Our PCR assay of gastric mucosa samples proved positive in 7 cases of group A (63.6%), whereas it always proved negative among group B subjects (100%). CONCLUSIONS: Our findings, apparently in contrast with the high sensitivity of PCR, may be attributed to the lower specificity of histology or, alternatively, the absence of H. pylori in the samples tested by PCR due to the patchy distribution of H. pylori colonization in the gastric mucosa. These observations are in agreement with those from other investigations.