Estimation of the window period of human T-cell leukemia virus type 1 and 2 tests by a lookback study of seroconverters among Japanese voluntary blood donors.

Background: Japan is endemic for human T-cell leukemia virus type 1 (HTLV-1), and the horizontal transmission of HTLV-1 is often reported. However, the window period (WP) for serologic or molecular screening is unclear.

Study Design And Methods: Results for anti-HTLV-1 screening and confirmatory tests obtained from 648 591 repeated blood donors in the Kyushu district, one of the most endemic areas of HTLV-1 in the world, were evaluated.