Helicobacter-negative gastritis: polymerase chain reaction for Helicobacter DNA is a valuable tool to elucidate the diagnosis.

BACKGROUND: Helicobacter-negative gastritis has been increasingly reported. Molecular techniques as the polymerase chain reaction (PCR) may detect bacterial DNA in histologically negative gastritis. AIM: To evaluate of Helicobacter PCR in gastric biopsies for the daily diagnostics of Helicobacter-negative gastritis. METHODS: Over a 5-year period, routine biopsies with chronic gastritis reminiscent of Helicobacter infection, but negative by histology, were tested by using a H. pylori specific PCR. Subsequently, PCR-negative samples were re-evaluated using PCR for other Helicobacter species. RESULTS: Of the 9184 gastric biopsies, 339 (3.7%) with histological-negative gastritis and adequate material were forwarded to PCR analysis for H. pylori and 146 (43.1%) revealed a positive result. In 193 H. pylori DNA-negative biopsies, re-analysis using PCR primers for other Helicobacter species, revealed further 23 (11.9%) positive biopsies, including 4 (2.1%) biopsies with H. heilmannii sensu lato. PCR-positive biopsies showed a higher overall inflammatory score, more lymphoid follicles/aggregates and neutrophils (P < 0.05). No Helicobacter DNA was found in control biopsies of 48 patients with neither primer set (P < 0.0001). In 274 patients with an endoscopic description, detection of H. pylori DNA was associated with ulcers and erosions (P < 0.01). Over all, in 339 histologically-negative gastric biopsies, Helicobacter DNA was detected in 169 (49.9%) samples with at least one primer set. CONCLUSION: Molecular testing offers a sensitive and specific diagnosis to a selected group of patients, in whom adequate searches for bacteria by conventional histology have resulted in the unsatisfactory diagnosis of H. pylori-negative gastritis.

Effect of buffered formalin on amplification of DNA from paraffin wax embedded small biopsies using real-time PCR.

BACKGROUND: The isolation of good quality DNA from routinely fixed and processed biopsy samples is crucial for the success of subsequent molecular analysis. AIMS: To compare the amount of beta actin DNA extracted from upper gastrointestinal tract biopsies fixed in buffered and unbuffered formalin. METHODS: Amounts of beta actin DNA extracted from forceps biopsies of the upper gastrointestinal tract fixed in unbuffered (n = 22) and buffered formalin (n = 16) were estimated by quantitative real-time polymerase chain reaction. RESULTS: The yield of beta actin DNA was significantly higher in biopsies fixed in buffered formalin than in those fixed in unbuffered formalin (median 2.8 x 10(4) and 5.3 x 10(2) DNA molecules, respectively; p < 0.005). Furthermore, fixation in buffered formalin led to a more reproducible DNA extraction, as indicated by the coefficient of variation (1.0 and 2.2, respectively). CONCLUSIONS: This study indicates that tissue samples should be fixed in buffered formalin to facilitate the use of molecular pathology analysis in routine biopsy material.