Serodiagnosis of viral hepatitis A by a modified competitive binding radioimmunoassay for immunoglobulin M anti-hepatitis A virus

Abstract

A competitive binding radioimmunoassay [RIA] (CBA) for antibody [human] to hepatitis A virus (HAV) was evaluated and compared with a standard solid-phase RIA for anti-HAV. CBA was sensitive and specific for the detection of anti-HAV, as demonstrated by the 98% concordance of CBA and solid-phase RIA test results. The standard CBA test was modified for the differential detection of acute (immunoglobulin [Ig] M) and convalescent (IgG) anti-HAV was preferentially absorbed with Staphylococcus aureus cells (protein A). The modified CBA (CBAM) test was capable of differentiating between acute- and convalescent-phase sera. The CBAM test detected IgM anti-HAV up to approximately 4 wk after the onset of illness.