AIM To detect hepatitis A virus-specific immunoglobulin M (IgM) antibody rapidly.METHODS Colloidal gold with an average dia-meter of 15 nm was prepared by controlled reduction of a boiling solution of 0.2 g/ L chloroauric acid with 10 g/ L sodium citrate and labeled with anti-HAVIgG as gold probe. Dot immunogold filtration assay (DIGFA) has been developed by coating anti-human μ 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.INTRODUCTIONHepatitis A virus-specific immunoglobulin M antibody (anti-HAV IgM) is the specific serological marker for the early diagnosis of acute hepatitis A. It can be detected by radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), solid phase hemagglutination inhibition test (SPHIA) and other methods. At present, double sandwich ELISA is in widespread use[1]. However, it takes more time to finish the test and the procedure is complicated. The need of a simple, rapid, and noninstrumented test is evident in many basic units, where laboratory facilities and trained personnel are limited. In 1989, Chun developed a rapid test, DIGFA[2]. It has been used to detect HCG, C-reactive protein, immunoglobulin G antibody and others[3,4]. We developed DIGFA for detection of anti-HAV IgM. The evaluation of this test is presented below.