Improvements in detection of antibody to hepatitis B core antigen by treating specimens with reducing agent in an automated microparticle enzyme immunoassay

Abstract

A fully automated microparticle enzyme immunoassay (EIA), lMx Core, was developed for the detection of antibody against hepatitis B core antigen (anti-HBc). IMx Core sensitivity was less than 0.5 Paul Ehrlich Institut units per ml and was greater than that of the commercial radioimmunoassay (RIA) or EIA, Corab and Corzyme, respectively. Specimens from blood donors and diagnostic and hospital patients, which included individuals with a variety of infectious and immune diseases, were tested in parallel by the IMx Core and EIA. Overall agreement of 99.1% (4,797 of 4,841) was obtained. Prevalence of anti-HBc tested by lMx Core ranged from 1.2% in volunteer blood donors to 9.1% in hospital laboratories. Discordant specimens reactive by IMx Core but negative by Corzyme or Corab resulted from the increased sensitivity of the IMx Core assay, since other hepatitis B markers were usually present. However, most discordant specimens were positive by the EIA or RIA but negative by IMx Core. No other hepatitis B markers could be detected in these discordants, and after addition of reducing agent, these specimens also became negative by EIA or RIA. In clinical trials, 30% (14 of 47) of volunteer blood donors and 8% (9 of 119) of hospital patients testing repeatedly reactive by the EIA had reduction-sensitive (unspecific) anti-HBc reactivity. The reducing agent, dithiothreitol, was added to each specimen automatically in the TMx assay to eliminate these unspecific reactions without significantly affecting anti-HBc reactivity resulting from hepatitis B virus infection as judged by the correlation with other hepatitis B markers.

A multicentre assessment of the specificity of ten anti‐HBc screening tests

“…One striking feature in this study was the high specificity exhibited by the Abbott IMx microparticle test for anti-HBc in samples referred for confirmation. Again, our data confirm the reports of others that this test has significantly improved specificity (Spronk et al, 1991;Aoki et al, 1993). A trial of an ELISA screening version of this test being developed by Abbott (Corzyme 2) and being evaluated at Newcastle RTC using the 1828 donations in this study resulted in only the 10 confirmed positives showing reactivity in this test.…”

“…As no direct 'neutralization' test was available to confirm the ELISA reactivities, a battery of supplementary assays was employed. Each referred sample was tested for anti-HBc by competitive radioimmunoassay (RIA) (Sorin Biomedica) because of the superior specificity of RIA (Schmidt et al, 1988;Parkinson et al, 1990), by a further anti-HBc test incorporating reducing agent (Abbott IMx) which has been reported to have improved specificity (Spronk et al, 1991). A haemagglutination titre was obtained using Corecell (International Reagents Corp., Kobe, Japan).…”

Hepatitis B virus infection and transfusion medicine: science and the occult

“…The addition of reducing agents to these assays, such as dithiothreitol or cysteine (as employed by the Abbott PRISM HBcore test), eliminates most false-positive reactions. [33][34][35] The factor responsible for this reductant-sensitive response appears to copurify with immunoglobulin M (IgM). It has characteristics of IgM anti-HBc even though it is found in patients who have not been exposed to HBV and thus, by definition, is nonspecific.…”

Chronic Hepatitis B Virus Infection in An Anti–Hbc-Nonreactive Blood Donor: Variant Virus or Defective Immune Response?

“…Results with the CORZYME and CORAB tests were nonreactive or borderline reactive ("gray" zone); the IMX Core test was nonreactive with all three samples. The IMX Core test uses a reducing reagent to eliminate nonspecific reactions and has a sensitivity of 0.4 to 0.5 Paul Ehrlich Institute (PEI) unitslml; the CORZYME EIA and CORAB RIA assays have sensitivities of 1.0 to 1.1 and 0.6 to 0.7 PEI unitdml, respectively (19).…”