Occult HBV Infection in Nigeria.

Occult hepatitis B virus infection (OBI) is manifested by presence of HBV-DNA in the absence of detectable Hepatitis B surface antigen (HBsAg) with or without anti-HBV antibodies. Hence it is a potential threat in blood transfusion medicine. This study was carried out to determine the prevalence of OBI as well as evaluate the effectiveness of using Hepatitis B surface antigen (HBsAg) marker alone in the diagnosis of HBV infection among HBsAg negative blood donors in Ilorin, Nigeria. A purposive sampling, including samples from 206 already donated and prescreened blood units from HBsAg negative from apparently healthy volunteer blood donors at the General Hospital Blood Transfusion Centre, Ilorin, Nigeria, were collected for further laboratory analysis for this study. Five millilitres of blood was collected and plasma sample tested for the presence of HBsAg using a commercially available ELISA kit. In addition, Polymerase Chain Reaction (PCR) was used for molecular detection of HBV DNA in each of the samples. Data was analyzed using descriptive statistics, Chi square at p = 0.05. Of the 206 HBsAg Micropoint® rapid kits pre-screened seronegative samples collected from the blood transfusion centre, 8 (3.9%) samples were positive for the presence of HBsAg when retested using ELISA in the laboratory. Eighteen of the 206 samples (8.7%) were HBV-DNA positive by a semi-nested PCR technique giving an OBI rate of 8.7%. Out of the 18 HBV-DNA positive samples, 17 (4.4%) were from males and only one (5.6%) was from a female donor. Analysis of the 18 HBV DNA positive samples using genotype specific primers into genotype A and Non-A showed that 15 (83.3%) were HBV genotype A, while 2 (11.1%) were genotypes other than A (Non-A), one (5.6%) sample had mixed genotypes (A & non-A). A prevalence of 8.7% OBI found in this study indicates substantial risk of post transfusion HBV infection in the study area in Nigeria. Hence, the need to include HBV DNA detection in the routine blood screening that is, using Nucleic Acid Testing (NAT) technique for transfusion safety in the country.