T he introduction of molecular methods to screen blood donors for hepatitis C virus (HCV), human immunodeficiency virus (HIV), and hepatitis B virus (HBV) has improved blood transfusion safety. [1][2][3] In addition, detection of molecular markers of infection in asymptomatic individuals with no serological markers, which are used for blood donor screening [hepatitis B surface antigen (HBsAg), anti-HCV, anti-HIV], provides new information on the natural course of these infections. Several aspects of the biology of HBV remain unclear. One of them is the detection of HBV DNA in the absence of HBsAg (occult HBV infection) and the determination of its frequency and characteristics. 4 Answering some of these questions became achievable in 2005 when HBV DNA screening of all seronegative blood donations was introduced in Poland. This report presents the analysis of such cases in asymptomatic blood donors identified during the first year of screening in a country with a medium level of HBV endemicity.The aim of this investigation was to analyze the frequency of HBV DNA-positive/HBsAg-negative donations and to use serological and molecular analysis of index samples and, when possible, follow-up and look-back samples to determine the HBV infection status of the donors. Materials and MethodsDonors and Sample Collection. The study was conducted in 2005, during which all blood donations collected in Poland were tested for anti-HCV (Ortho

The HCVcAg test proved to be feasible for routine screening in the Polish Blood Transfusion Service. Six HCVcAg RR/anti-HCV-negative donors were identified. The calculated residual risk in this study of donors in the preseroconversion window was 45 per million. Mandatory testing of every blood and plasma donation for HCVcAg or HCV RNA was recommended as of January 2, 2002.

The frequency of wp donors is 18.5 per 1 million. The unexpected high frequency of Genotype 4 and Subtype 3a and the low frequency of Subtype 1b was observed in wp donors compared to anti-HCV-positive individuals. Additional epidemiologic questioning introduced after HCV RNA detection may help to identify infection source.

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