Evaluation of enzyme-linked immunosorbent assay for quantitation of antibodies to Japanese encephalitis virus in swine sera.

Enzyme-linked immunosorbent assay (ELISA) was evaluated for the quantitation of antibodies to Japanese encephalitis virus in swine sera. The assay was highly reproducible (coefficient of variation of the absorbance values obtained with positive sera was less than 3.4%) and was significantly correlated with the conventional haemagglutination inhibition (HI) test (correlation coefficient was 0.944). The statistical analysis based on the frequency distribution of the absorbance values for 366 swine serum samples gave 0.204 as a feasible borderline to differentiate positive sera from negative sera. Using this criterion, all of the sera positive for HI antibody were found positive for antibody by ELISA and also all negative sera by ELISA were negative by HI. Inconsistent results were found in only six cases (1.6%).