Evaluation of an antigen‐capture EIA for the diagnosis of hepatitis E virus infection

Summary An enzyme immunoassay ( EIA ) has been developed for hepatitis E virus ( HEV ) antigen ( HEV ‐ A g) detection and marketed in C hina. This study aimed to evaluate the sensitivity of the assay and assess the value of HEV ‐ A g detection in the diagnosis of HEV infection in comparison with HEV RNA detection. Using serial dilutions of a genotype 4 HEV strain, significant correlation was found between the EIA ( S / CO ) and HEV RNA (IU/mL) concentration in the range 10 3.5 to 10 0.5 IU/mL HEV RNA , the P earson correlation coefficient r approached 0.97. The EIA detection limit was 54.6 IU/mL, compared to 24 IU/mL for HEV RNA using real‐time RT ‐ PCR . In clinical samples from hepatitis E patients, the HEV ‐ A g and HEV RNA positivity rates were 55.6% (65/117) and 60.7% (71/117) in sera and 76.7% (56/73) and 84.9% (62/73) in stools, and the concordance of these two markers was 77.8% in sera and 80.8% in stools. In serum samples, the HEV ‐ A g positivity rate and the concordance between HEV ‐ A g and HEV RNA were inversely proportional to the presence of anti‐ HEV antibody. The presence of anti‐ HEV I g G could reduce the S / CO of the HEV ‐ A g EIA . These results reveal a significant correlation between the detection of HEV ‐ A g and HEV RNA . The sensitivity of the HEV ‐ A g EIA was lower than real‐time RT ‐ PCR but could be higher than conventional nested RT ‐ PCR . Therefore, the detection of HEV ‐ A g in serum and faeces is valuable for the diagnosis and prognosis of HEV infection in developing regions where real‐time RT ‐ PCR is not available.