Evaluation of dot immunogold filtration assay for anti-HAV IgM antibody

AIM:To detect hepatitis A virus-specific immunoglobulin M (IgM) antibody rapidly.METHODS:Colloidal gold with an average diameter of 15nm was prepared by controlled reduction of a boiling solution of 0.2g/L chloroauric acid with 10g/L sodium citrate and labeled with anti-HAVIgG as gold probe. Dot immunogold filtration assay (DIGFA) has been developed by coating anti-human &mgr; chain on nitrocellulose membrane (NCM) for capturing the anti-HAV IgM in serum, then using cultured hepatitis A antigen as a bridge , connecting anti-HAV IgM in sample and anti-HAV IgG labeled colloidal gold. If there was anti-HAV IgM in sample, gold probes would concentrate on NCM, which will appear a pink dot.RESULTS:A total of 264 serum samples were comparatively detected with both DIGFA and ELISA by blind method. Among them, 88 were positive and 146 were negative with the two methods. The sensitivity and the specificity of DIGFA were 86.27% and 90.12%, respectively. Fifteen negative serum samples and 15 positive serum samples were detected 3 times repeatedly, the results were the same.CONCLUSION:DIGFA is a simple, rapid, sensitive, specific and reliable method without expensive equipment and is not interfered with rheumatoid factor (RF) in serum. It is suitable for basic medical laboratories. The test could be applied for diagnosis and epidemiological survey of hepatitis A. It has a broad prospect in application.