Performance of an antigen assay for diagnosing acute hepatitis E virus genotype 3 infection.

BACKGROUND: Hepatitis E virus (HEV) is a major cause of hepatitis worldwide. Its diagnosis is based on the detection of anti-HEV IgM and/or HEV-RNA. OBJECTIVE: To evaluate the performance of the Wantaï HEV-antigen (Ag) ELISA(Plus) assay for diagnosing acute HEV infections. STUDY DESIGN: Specificity was assessed using 100 blood samples containing no anti-HEV IgM, anti-HEV IgG, or HEV-RNA. Cross reactivity was assessed using samples positive for hepatitis C virus RNA (n=10), Epstein-Barr virus DNA (n=10) and cytomegalovirus DNA (n=10). Serial dilutions of 4 HEV RNA positive samples were used to estimate the corresponding viremia detected with the Ag assay. Blood samples from 33 immunocompetent and 31 immunocompromised patients with an acute HEV genotype 3 infection, HEV-RNA positive, were tested to assess diagnostic sensitivity. RESULTS: The HEV-Ag assay was 100% specific, with no cross-reactivity. The lower viremias detected ranged from 10(3)copies/ml to 10(5)copies/ml (800-80,000UI/ml). Diagnostic sensitivity for an acute HEV infection was 91%, with no significant difference between immunocompetent (88%) and immunocompromised (94%) patients. The HEV-Ag assay was more frequently positive in immunocompromised patients at the acute phase (94%) than was the anti-HEV IgM test (71%; p=0.04). The HEV-Ag assay ratio was correlated with HEV-RNA viral load (ρ=0.54; p<0.0001). CONCLUSION: The HEV-Ag assay performed well and could be suitable for laboratories with no molecular diagnosic facilities.