Application of Stool-PCR test for diagnosis of Helicobacter pylori infection in children

AIM:To evaluate the usefulness of stool-PCR test for diagnosis of Helicobacter pylori(H pylori)infection in pediatric populations. METHODS:Based on endoscopic features(including nodular gastritis,erosive duodenitis and ulcer)and/or a positive rapid urease test(RUT)obtained during endoscopy,28 children from a group of children admitted to the Children’s Medical Center of Tehran for persistent upper gastrointestinal problems were selected to compare biopsy-based tests with stoolPCR.Their gastric activity and bacterial density were graded by the updated Sydney system,and their first stool after endoscopy was stored at-70℃.Biopsies were cultured on modified campy-blood agar plates and identified by gram-staining,biochemical tests,and PCR.Two methods of phenol-chloroform and boiling were used for DNA extraction from H pylori isolates. Isolation of DNA from stool was performed using a stool DNA extraction kit(Bioneer Inc,Korea).PCR was performed using primers for detection of vacA,cagA,and 16srRNA genes in both isolates and stool. RESULTS:Sixteen out of 28 child patients(57%) were classified as H pylori positive by biopsy-based tests,of which 11(39%)were also positive by stoolPCR.Sensitivity and specificity of stool-PCR was 62.5% and 92.3%respectively.H pylori was observed in histological sections for 10 out of 11 stool-positivepatients.Association was observed between higher score of H pylori in histology and positivity of stoolPCR.Also association was observed between the more severe form of gastritis and a positive stool-PCR. CONCLUSION:Association between higher score of H pylori in histology and a positive stool-PCR make it a very useful test for detection of H pylori active infection in children.We also suggest that a simple stool-PCR method can be a useful test for detection of H pylori virulence genes in stool.