Background: Commercial serological tests for the detection of Helicobacter pylori infection must be locally validated. We evaluated the accuracy of five commercial tests in the Chinese population. Methods: Serum samples were collected from patients referred for upper endoscopy. Antral biopsies were taken for histological examination and culture of H. pylori. The gold standard for diagnosing H. pylori infection was positive histological staining and/or positive H. pylori culture. The serum samples were tested for H. pylori antibodies using the following tests: (i) Cobas Core Anti‐H. pylori EIA; (ii) GAP IgG; (iii) GAP IgM; (iv) H. pylori microwell EIA (Quidel); and (v) Premier H. pylori. The sensitivity, specificity and accuracy of each test was calculated according to the manufacturers’ instructions or according to a new cut‐off value. Results: A total of 158 patients were recruited amongst whom 114 (72%) were H. pylori‐positive. Indeterminate results varied from 7% to 19%. The accuracy of the tests varied from 57% to 85%. By using new cut‐off values, the accuracy was much improved, ranging from 73.4% to 86.7%. Conclusions: By defining new cut‐off values for the Chinese population, we were able to improve the performance of some of the serology tests. This illustrates the importance of local validation.

SUMMARYAim: To investigate the efficacy of measurement of Helicobacter pylori stool antigen (HpSA) using stored frozen stool specimens, and to assess whether there were factors affecting efficacy in Hong Kong. Methods: Patients undergoing upper endoscopy at Tuen Mun Hospital were recruited. Stool samples were saved for HpSA testing and questionnaires were completed. Stool samples were frozen immediately upon receipt and stored at ) 70°C until tested. HpSA results were compared with rapid urease test and histology. Results: One hundred and eighty-one patients were recruited. One hundred and seventy-eight patients were suitable for analysis. Eighty-three were H. pylori positive and 95 were H. pylori negative. The mean duration of storage of the stool samples was 120 days (range, 40-225 days). The sensitivity, specificity and positive and negative predictive values were 84.3%, 97.9%, 97.2% and 88.6%, respectively. In patients with a false negative HpSA test, there was a significant delay in collecting the stool specimen after endoscopy when compared with those with a true positive HpSA test (4.2 vs. 2.3 days; P < 0.05). However, the duration of storage of the specimens was not longer, and consumption of coffee or tea and smoking habits were similar. Conclusions: HpSA testing showed good sensitivity and specificity, even with frozen stool samples stored for up to 225 days. The efficacy was not affected by coffee, tea or smoking.