TRANSFUSION‑TRANSMITTED HBV INFECTION THROUGH PLATELET CONCENTRATE DONATED DURING THE WINDOW PERIOD AFTER INTRODUCTION OF THE NUCLEIC ACID AMPLIFICATION TEST

We experienced a case of HBV infection transmitted through platelet concentrate donated during the window period. Nucleic acid amplification test(NAT)has been performed since February 2000 using 50-pooled samples. The donor was found to be positive by individual nested PCR using stored samples in a retrospective study. The HBV DNA concentration was 2,800 copies ml in the blood. The patient was a 3-year-old boy with acute myeloid leukemia and was negative for HBsAg at notification. Although we injected him with anti-HBs IgG, he became positive for HBsAg 6 months after the infected blood transfusion. He subsequently developed acute hepatitis and progressed to protracted viral infection. HBV nucleotide sequences of the patient and donor were identical. He received allogeneic peripheral blood stem cell transplantation from his HLA-identical mother 11 months after the infected blood transfusion. As the mother was negative for anti-HBs antibody, immunization with HBV vaccination was performed before stem cell harvest. Although the incidence of transfusion-transmitted HBV infection has decreased through the introduction of NAT, this case indicates that NAT using 50-pooled samples may not be effective for the detection of very early-stage HBV infection.