Improvement in the specificity of assays for detection of antibody to hepatitis B core antigen.
Reducing agents dramatically alter the specificity of competitive assays for antibody to hepatitis B core antigen (anti-HBc). A specificity improvement was demonstrated with a new assay which utilizes microparticle membrane capture and chemiluminescence detection as well as a current radioimmunoassay procedure (Corab: Abbott Laboratories, Abbott Park, Ill.). The effect was most noticeable with elevated negative and weakly reactive samples. In both systems, reductants increased separation of a negative population (n = 160) from assay cutoffs. With a selected population (n = 307), inclusion of reductant eliminated apparent anti-HBc activity in 54 of 81 samples in the 30 to 70% inhibition range. Reductant-stable anti-HBc samples were strongly associated with the presence of antibody to hepatitis B surface antigen (21 of 27). The association persisted below the detection limits of current assays to 0.3 to 0.4 Paul Ehrlich Institute units per ml. Only 1 of 54 reduction-sensitive borderline samples was confirmed to be positive for antibody to hepatitis B surface antigen. The modified procedures had unchanged or slightly improved sensitivity for immunoglobulin G (IgG)-associated anti-HBc activity. Although IgM anti-HBc detection was reduced from four- to eightfold in the presence of reductants, sensitivities remained at least twofold greater than tha of an enzyme immunoassay (Corzyme M; Abbott) designed to detect acute-phase levels of IgM anti-HBc. The use of reducing agents should significantly improve the reliability of anti-HBc testing, especially near assay cutoffs.
Weare
J A
JA
Abbott Laboratories, Abbott Park, Illinois 60064.
Robertson
E F
EF
Madsen
G
G
Hu
R
R
Decker
R H
RH
D001667:Binding, Competitive; D005069:Evaluation Studies as Topic; D006509:Hepatitis B / Q000175:diagnosis / Q000276:immunology; D006510:Hepatitis B Antibodies / Q000097:blood*; D006512:Hepatitis B Core Antigens; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000032:analysis; D007075:Immunoglobulin M / Q000032:analysis; D008163:Luminescent Measurements; D010084:Oxidation-Reduction; D011863:Radioimmunoassay; D012680:Sensitivity and Specificity
D006510:Hepatitis B Antibodies; D006512:Hepatitis B Core Antigens; D007074:Immunoglobulin G; D007075:Immunoglobulin M