DIFFERENTIAL-DIAGNOSIS OF ACUTE HBSAG POSITIVE HEPATITIS USING IGM ANTI-HBC BY A RAPID, FULLY AUTOMATED MICROPARTICLE ENZYME-IMMUNOASSAY

Background/Aims: We determined the diagnostic significance of IgM anti -HBc by a rapid, fully automated microparticle enzyme immunoassay (IMx CORE-M) in acute HBsAg positive hepatitis. Methods: We studied prospe ctively for at least 6 months 100 patients with acute self-limited hep atitis B (group A) and 40 patients with acute hepatitis superimposed o n histologically confirmed chronic hepatitis B (group B). On admission , all patients in group A were positive and those in group B were nega tive for IgM anti-HBc by a commercially available enzyme immunoassay. Results: Based on the assay criteria, the rates of IMx CORE-M (>1.2) p ositive serum samples on admission, 4, 12 and 24 weeks later were: in group A: 100%, 95%, 72%, 44% and in group B: 20%, 27.5%, 17.5%, and 15 %, respectively. Misclassification was observed in 20-27.5% of the acu te on chronic hepatitis cases. However, the mean IMx CORE-M index valu e was found to be significantly higher in group A during the whole fol low-up. In particular, on admission the mean IMx CORE-M index value wa s 2.504+/-0.435 (range: 1.508-3.482) in group A and 0.747+/-0.346 (ran ge: 0.062-1.384) in group B (p<0.001). Discriminant function analysis showed that the cutoff level between the two groups for IMxCORE-M inde x on admission was 1.5. Four to 12 weeks from admission, in the group with acute on chronic hepatitis B cases, 13 patients with HDV and/or H CV superinfection had significantly lower IMx-CORE M index values comp ared with 27 patients with acute hepatitis due to exacerbation of chro nic hepatitis B. Conclusions: IMx CORE-M appears to be an accurate dia gnostic test to differentiate acute from acute on chronic HBsAg positi ve hepatitis, but the cut-off level seems to be higher (1.5 instead of 1.2).