The role of anti-HBc IgM screening of blood donors

Abstract

Dear Editor, I read with interest the article ‘The Role of anti-HBc IgM Screening of Blood Donors’ [1]. Authors recommend screening of blood donors for antibody to hepatitis B core antigen (anti-HBc) IgM class in addition to hepatitis B surface antigen (HBsAg) for reduction of residual risk of transfusion transmitted hepatitis B virus (TT-HBV) infection. Traditionally ‘anti-HBc alone’ has been studied extensively in blood donors. ‘anti-HBc alone’ denotes presence of anti-HBc (total) in absence of HBsAg and anti-HBs (antibody to HBsAg). Studies from countries with moderate endemicity of HBV infection reported HBV-DNA in 20-67% of blood donors with ‘anti-HBc alone’ [2,3]. Rarely donors with anti-HBc and anti-HBs were reported with HBV-DNA [3]. In contrast, authors are first to recommend anti-HBc IgM for screening of blood donors. Authors hypothesis is based on the fact that the anti-HBc IgM appears first thus making it suitable for screening. It is simplistic view of perplexing serological and virological events associated with HBV infections and clinical syndromes. Anti-HBc IgM is known to have major role in diagnosis of acute as compared to chronic HBV infection of carrier state including HBsAg (Hepatitis B e Antigen) negative HBV infections [4]. Anti HBc IgM also has limited utility to diagnosis of chronic HBV infections with mutant strains and such infections are not uncommon in our country [5]. Thus anti-HBc IgM screening will result in low yield in blood donors [6]. A study undertaken from January to June 2005 (unpublished data) contradicts hypothesis of IgM anti-HBc in blood screening. A total 476 voluntary blood donors were enrolled for the study. They were healthy male, free from infections as per current National Blood Transfusion guidelines. Donors were HBs Ag negative and did not give past history of jaundice (deferral rate of 2.1% and 1.9% respectively). They were screened for anti-HBc (total) by Enzyme Immune Assay (EIA) of which 48 (10.1%) tested positive. These 48 subjects were assayed for anti-HBs and anti-HBc IgM by EIA (Table 1). It was concluded that 4.4% (21/476) donors were ‘anti-HBc alone’. 2.1% (10/476) donors were anti-HBc IgM positive and they represented only 19.0% (4/21) of ‘anti-HBc alone’ donors. Thus 81% (17/21) of potentially infectious ‘anti-Hbc alone’ donors would have been overlooked with anti-HBc IgM assay. Table 1 Anti-HBs and anti-HBc IgM status in anti HBc (total) positive blood donors Of course, there is unanimity in necessity for additional screening of blood donors in reducing residual risk of TT-HBV. However, anti-HBc IgM in blood donor screening may not be beneficial. In this background, it will be prudent to undertake a multi-centric study correlating anti-HBc (total and IgM), anti-HBs and HBV-DNA in blood donors for policy formulation. Till such time, it is recommended that ‘anti-Hbc alone’ positive blood units should be discarded.