Performance Characteristics of Microparticle Enzyme and Chemiluminescence Immunoassays for Measurement of Anti-HBc Immunoglobulin M in Sera of Patients with HBeAg-Negative Chronic Hepatitis B Virus Infection

Abstract

The IMx, AxSym, and Architect immunoglobulin M anti-HBc assay systems for detecting hepatitis B virus e antigen-negative chronic hepatitis B virus infection were compared. Despite good intra-and interassay coefficients of variation, significantly different values and low correlation (overestimation by AxSym and underestimation by Architect) were observed. Association and cutoff values for distinguishing patients with viral replication should be established for all methods.In patients with hepatitis B virus e antigen (HBeAg)-negative chronic hepatitis B virus (HBV) infection, absolute levels and changing titers of immunoglobulin M antibodies against the HBV core protein (anti-HBc IgM) are considered markers of viral replication (11,13,17). The measurement of anti-HBc IgM is an easily performed and inexpensive alternative to frequent serum HBV DNA measurements for monitoring untreated patients, as well as patients treated with alpha interferon or antiviral agents (1, 5, 11-13, 15-18, 20).Most experience in the detection of anti-HBc IgM in patients with chronic hepatitis B (CHB) is based on microparticle enzyme immunoassays (MEIA) using the IMx analyzer. Most anti-HBc IgM values for patients with HBeAg-negative chronic HBV infection are below the cutoff limit for a diagnosis of acute hepatitis B, either in the negative or in the "gray" zone. When determined by a classic enzyme-linked immunosorbent assay, they range from 20 to 600 U/ml (10), and when tested with a MEIA (the IMx system), the results range from index values of 0.2 to 2.0, approximately 10 to 300 U/ml (1, 7).In most laboratories, the IMx analyzer has been replaced by the AxSym analyzer (MEIA), and newer analyzers with chemiluminescent assays (CMIA) are gradually being instituted (4, 6, 21). We compared the anti-HBc IgM measurements by the three analyzers for patients with HBeAg-negative chronic HBV infection.The IMx (MEIA), AxSym (MEIA), and Architect (CMIA) analyzers (Abbott Laboratories, Abbott Park, IL) were used for anti-HBc IgM quantification. The results of the MEIA are expressed as index values (ratio of sample to calibrator) (9), and the results of the CMIA are in relative light units divided by the cutoff value determined in the preceding calibration (21).For the evaluation of the inter-and intra-assay variation (coefficient of variation [CV]), we used multiple aliquots of sera from three patients with HBeAg-negative CHB (patients P1 to P3). Each serum sample was tested five times in the same assay and five times over five days with each of the three analyzers. Anti-HBc IgM measurements for 53 consecutive patients with HBeAg-negative chronic HBV infection were compared. The influence of rheumatoid factor (RF) measured by nephelometry (Immage immunochemistry systems; Beckman Coulter, Inc., Fullerton, CA) was assessed.For data entry, frequencies, and comparisons, SPSS version 14.0 (SPSS, Inc., Chicago, IL) was used. The t test and the Mann-Whitney test were applied for parametric and nonparametric data comparisons, respectively. For paired compa...