The study shows that more than 17 percent of healthy, young blood donors in Pakistan are already exposed to HBV, with two-thirds showing anti-HBs levels of greater than 100 mIU per mL. One in 200 blood donors who are HBsAg-, anti-HBc-positive, however, have occult HBV infection, with likelihood of transmission of hepatitis B in recipients of blood components derived from them. HBsAg-negative individuals who are anti-HBc-negative and those who are anti-HBc-positive, anti-HBs-positive, and HBV DNA-negative should be selected as regular blood donors to minimize transmission due to occult hepatitis B infection.

NAT has improved the safety of blood products at our transfusion institution. Confirmation of NAT results must always be done either on follow-up samples or on samples from the retrieved frozen plasma bag.

BackgroundThe prevalence of chronic Hepatitis B Virus (HBV) infection is 2–4% in the Pakistani population, defining Pakistan as an intermediate prevalence country. In this study, hepatitis B surface antigen (HBsAg) reactive blood donations were screened using a combination of serological and molecular methods to identify immune escape HBV mutant strains and to determine the HBV genotypes and subtypes present in Pakistan.MethodsBlood donations were collected at the Armed Forces Institute of Transfusion (AFIT) located in northern Pakistan and the Hussaini Blood Bank (HBB) located in the south. From 2009 to 2013 a total of 706,575 donations were screened with 2.04% (14,409) HBsAg reactive. A total of 2055 HBsAg reactive specimens, were collected and screened using a monoclonal antibody based research assay to identify immune escape mutants followed by PCR amplification and DNA sequencing to identify the mutation present. DNA sequences obtained from 192 specimens, including mutant candidates and wild type strains, were analyzed for escape mutations, genotype, and HBsAg subtype.ResultsMutations were identified in approximately 14% of HBsAg reactive donations. Mutations at HBsAg amino acid positions 143–145 are the most common (46%) with the mutation serine 143 to leucine the most frequently occurring change (28%). While regional differences were observed, the most prevalent HBV strains are subgenotypes of D with subgenotype D1/subtype ayw2 accounting for the majority of infections; 90.2% at AFIT and 52.5% at HBB.ConclusionsThe high frequency of immune escape HBV mutants in HBV infected Pakistani blood donors highlights the need for more studies into the prevalence of escape mutants. Differences between vaccinated and unvaccinated populations, the correlation of escape mutant frequency with genotype, and impact of escape mutations in different genotype backgrounds on the performance of commercially available HBsAg assays represent avenues for further investigation.