The Helico-Blot 2.1 (Genelabs Diagnostics, Singapore) was used to test the ELISA-positive serum samples from both groups. The test is based on Western blot assay of H pylori whole-cell antigens that is made from bacterial lysate of a strain of H pylori that is known to cause ulcers. Strips were marked at the 116 (CagA), 89 (VacA), 37, 35, 30 and 19.5 kDa antigen lines and at an additional antigen line, designated the current infection marker (CIM). The recommended criteria for determining H pylori seropositivity as specified by the manufacturer is any one of:
• the detection of 116 kDa (CagA) band with one or more bands of 89, 37, 35, 30 (UreA) and 19.5 kDa together, or with CIM;
• any one band of the 89, 37 or 35 kDa, with or without the CIM; or
• detection of both the 30 and 19.5 kDa bands, with or without the CIM.
Imaging and analysis of immunoblots were done using Gel Doc 2000 and Quantity One quantification software (BioRad, USA).
Data were analyzed using SPSS 10.1 (SPSS Inc, USA). P<0.05 was considered to be statistically significant.