The diagnosis of acute viral hepatitis A or B by microparticle enzyme immunoassay

The traditional approach to the diagnosis of viral hepatitis has been to collect a serum sample and to test it for the presence of hepatitis B surface antigen (HBsAg), IgM to the core of HBV (anti-HBc IgM) and IgM to HAV (anti-HAV IgM) by solid phase radio- or enzyme immunoassays. Microparticle enzyme immunoassay technology (IMx®-Abbott Laboratories) has been introduced as an automated carousel system for the detection of these markers. A side-by-side, blinded comparison of IMx to current IA was performed for HBsAg on 659 specimens submitted from March to July 1990, of which 72 (10.8%) were positive by AUSRIA (Abbott RIA for HBsAg) and 2 of these were discordant in IMx. Both were near the cutoff and by confirmatory testing one was positive and the other negative. Forty three percent (25/58) of frozen stored sera tested for anti-HBc IgM, by IMx, were positive by EIA (Corzyme M). One specimen near the cutoff was negative by EIA but weakly positive by IMx. Anti-HAV IgM was found in 21.8% (46/211) of sera with 100% correlation by IMx. Thus IMx had the following percent sensitivities and specificities: HBsAg; 98.6, 99.9; anti-HBc IgM; 100, 99.9; anti-HAV IgM; 100, 100. The test set-up times for the 3 markers in the IMx were similar to the RIA and EIA. The turnover time was 45 min for a full IMx carousel compared to: AUSRIA-short incubation (4 h), or long incubation (14 h); Corzyme M-short (4.75 h) or long (20 h); anti-HAV IgM (23 h). With equal accuracy to existing tests, the benefit of IMx technology resides in simplicity and saving of technologist time.