Italian blood donors with anti-HBc and occult hepatitis B virus infection

From the Banca del Sangue e del Plasma, A.O. S. Giovanni Battista di Torino, Italy (PMan, FD, AP, CV, FCa, FCu); Immunoematologia e Medicina Trasfusionale, Ospedale di Ivrea, Italy (MG); S.O.C. di Medicina Trasfusionale, ASL 14, Presidio Ospedaliero di Domodossola (RB); Immunoematologia, A.S. Torino 4, Italy (OG); Medicina Trasfusionale ed Immunoematologia, Casale Monferrato, Italy (RG); Servizio di Immunoematologia e Trasfusionale, Osp. di Verbania, Italy (ML); Servizio di Immunoematologia e Trasfusionale, Ospedale SS. Annunziata-ASL 17, Savigliano, Italy (DT); Centro Trasfusionale, OIRM S. Anna di Torino, Italy (PG); Servizio di Immuno-ematologia e Trasfusione, A.O. Ospedale Maggiore della Carità di Novara, Italy (MV); SCDU Immunologia dei Trapianti, Università di Torino, Italy (PMag); SCDU Gastroenterologia ed Epatologia, Università di Torino, Italy (MLA, AS, MR) Correspondence: Paola Manzini, Banca del Sangue e del Plasma, A.O. S. Giovanni Battista di Torino, Corso Bramante 88, 10126 Torino, Italy. E-mail: pmanzini{at}molinette.piemonte.it Background and Objectives: Occult hepatitis B virus (HBV) infection might allow the release of viremic units into the blood supply network if blood is tested only for hepatitis B surface antigen (HBsAg). The aim of our study was to evaluate the actual prevalence, viral load and genotype of occult HBV infections among first-time blood donors in north-western Italy and to suggest a way to minimize risks of transmission of this infection. Design and Methods: We assayed 6313 consecutive blood donors for antibodies to HBV core antigen (anti-HBc) in addition to mandatory screening. HBsAg-negative/anti-HBc-positive donors were assayed for antibodies to HBsAg (anti-HBs) and for HBV-DNA using COBAS Ampliscreen HBV (Roche TM ) on individual donations. All HBV-DNA-positive samples underwent confirmatory testing with additional polymerase chain reaction-based assays. Results: The prevalence of anti-HBc positive subjects was 4.85%. Fourteen out of 288 blood donors (4.86%) were confirmed to have circulating HBV-DNA at a low level (range 8–108 IU/mL). All viremic donors were also anti-HBs-positive. Interpretation and Conclusions: We estimate that in north-western Italy up to 2298 units per million donated units from first-time donors may contain HBV-DNA. The risk of an HBV-DNA positive unit from an occult carrier being released into the blood supply is more than 100 times higher than the estimated residual risk related to the windo