Histological and clinical predictive value of determination of tissue CagA status by PCR in Helicobacter pylori infected patients; results of the large population based study in western Turkey.

BACKGROUND/AIMS: Early experimental and epidemiological studies have suggested that the presence of cagA gene was a virulence factor for Helicobacter pylori. We aimed to investigate the clinical significance of tissue CagA status in Helicobacter pylori infected patients and to assess its association with histological changes in gastric mucosa. METHODOLOGY: Three hundred and forty-five patients with Helicobacter pylori infection established by both urease test and histological examination were included in the study. The symptoms of the patients were recorded according to the Glasgow dyspepsia scale. Biopsies (cardia, corpus, angulus and antrum) were evaluated histologically according to the Sidney system. The cagA status was determined by polymerase chain reaction method from an antral biopsy. Polymerase chain reaction studies were performed by Wizard genomic DNA purification system (promega). We also determined the serum levels of tumor necrosis factor-alpha, and gastrin. They were all prescribed lansoprazole (30 mg b.i.d.), clarithromycin (500 mg b.i.d.), and amoxycillin (1 g b.i.d.) for a week. At the 8th week a second endoscopy was performed and further biopsy specimens were obtained from the same sites. Mann-Whitney U and chi 2 tests were used for statistical analyses. RESULTS: Two hundred and thirty-five patients (68.1%) were infected with cagA-positive strains of Helicobacter pylori and the other 110 patients (31.8%) were infected with cagA-negative strains. We compared the parameters and measurements studied in this trial between the patients infected with cagA-positive and negative Helicobacter pylori strains. Helicobacter pylori density was greater in the cagA-positive group by 1.9 +/- 0.9 than in the cagA-negative group by 1.2 +/- 0.7 (P = 0.01). Helicobacter pylori activity and chronic inflammation also were significantly higher in the cagA-positive group with the values of 1.4 +/- 0.8 and 2.1 +/- 1.1 than in the cagA-negative group with 0.7 +/- 0.2 and 1.3 +/- 0.5, respectively (P = 0.001, P = 0.002). The presence of atrophy and lymphoid aggregate was not different between the two groups (P > 0.05). However intestinal metaplasia was shown to be significantly frequent in patients infected with cagA-positive Helicobacter pylori strains (0.001). Serum tumor necrosis factor-alpha and gastrin levels which were accepted as the markers of inflammation in Helicobacter pylori infection were increased in the cagA-positive group compared with the cagA-negative group. Serum tumor necrosis factor-alpha level was 11.3 +/- 7.0 pg/mL in the cagA-positive group and 4.9 +/- 2.7 pg/mL in the cagA-negative group (P = 0.001). Gastrin level also showed a significant difference between two groups by 66.8 +/- 31.1 pg/mL and 37.2 +/- 19.2 pg/mL, respectively, in the cagA-positive and negative groups (P = 0.001). The virulent strains seem to cause peptic ulcer more frequently. Peptic ulcer was determined in 17% of patients in the cagA-positive group but this ratio was 9% in the cagA-negative group (P = 0.608). Although, all these differences of the degree of inflammation, clinical spectrum and biochemical parameters were seen, interestingly there was no significant difference in the severity of the symptoms of the patients in both groups according to Glasgow dyspepsia severity score (P = 0.20). CONCLUSIONS: Our results confirm that cagA-positive strains of Helicobacter pylori cause greater histological changes. However this virulence is not associated with more severe symptoms. The histological changes can be predictable by determining the tissue cagA status.