Enzyme immunoassay for detection of total and IgM-specific antibodies to hepatitis A virus and its clinical application.

Antibody to hepatitis A virus (anti-HAV) and IgM class antibody to HAV (IgM anti-HAV) in sera from 73 patients with hepatitis A and from 550 normal subjects were measured by enzyme immunoassay (EIA) and the results were compared with those of radioimmunoassay (RIA). Since RIA has the disadvantage of requiring radioisotopes and special equipment, the clinical applicability of EIA and possible methodological problems were evaluated. The EIA for anti-HAV showed an excellent correlation with RIA, indicating its usefulness for the demonstration of the immune status in these subjects. Positive results of anti-HAV were obtained in the early stage after the onset of hepatitis A. However, pretreatment for inactivation of samples was required. False-positive reactions were found in sera to which sodium azide was added as preservative. In the measurement of IgM anti-HAV, a fundamental study revealed quite satisfactory results, correlation with the results of RIA was excellent. In patients with hepatitis A, the titers reached a peak in the second to third week, followed by a gradual decline. Changes to a negative reaction were never encountered within three months. We concluded that the EIA is an useful tool in the diagnosis of hepatitis A and can replace RIA.