Hepatitis B virus (HBV) infection with its associated sequel is a disease of major public health importance, being the 10th leading cause of death globally [1, 2]. HBV infection accounts for 500,000 to 1.2 million deaths each year . Of the approximately 2 billion people infected worldwide, more than 350 million are chronic carriers of HBV . Approximately 15-40% of infected patients will develop cirrhosis, liver failure or hepatocellular carcinoma (HCC) [5, 6]
The aetiological agent (Hepatitis B virus) is a member of the family Hepadnaviridae and the genus Orthohepadnavirus . It is a double stranded circular DNA virus composed of an outer envelope containing hepatitis B surface antigen (HBsAg) and an inner nucleocapsid consisting of hepatitis B envelope antigen (HBeAg) and hepatitis B core antigen (HBcAg). Corresponding antibodies to each of these antigens are Hepatitis B surface antibody (anti-HBs or HBsAb), Hepatitis B envelope antibody (anti-HBe or HBeAb) and hepatitis B core IgM and IgG antibody (anti-HBc or HBcAb) . The viral core also contains double stranded DNA genome and DNA polymerase. The serological markers of Hepatitis B virus are HBsAg, anti-HBs, HBcAg, anti-HBc (IgM and IgG), HBeAg, anti-HBe, and HBV DNA; these are important as they can be used in the diagnosis of the infection and to determine the severity of the infection .
Following infection by the hepatitis B virus (HBV), the first serological marker to appear in the blood is the HBV DNA, followed by HBsAg, the DNA polymerase and HBeAg. Thereafter, the antibodies to the hepatitis B antigens (HBcAb, HBeAb and HBsAb) can be detected. Screening of donated blood by enzyme-linked immunosorbent assay (ELISA) for HBsAg is the common method for detecting hepatitis B infection . Screening of blood for the detection of this viral marker, however, does not rule out the risk of transmission of hepatitis B totally, because during the host serological response to infection, there is a phase during which the HBsAg cannot be detected in the blood although hepatitis B infection is present. This phase is known as the 'window period'. It represents a carrier state of the disease.
Findings indicate that testing done for HBsAg alone is not sufficient to eliminate HBV infection from blood supply [10–13]. A marker which would be indicative of hepatitis B infection during the window period is thus of paramount importance in blood banking especially in low income country like Nigeria, where DNA testing of all collected units of blood is not feasible.
This study was therefore designed to evaluate the reliability of using HBsAg marker alone, in diagnosis of HBV infection among blood donors and to detect the presence of a marker which would be indicative of hepatitis B infection during the window period.