Seroindeterminate HTLV-1 prevalence and characteristics in blood donors in Taiwan.

Human T-cell leukemia virus type 1 (HTLV-1) is commonly accepted as the cause of adult T-cell leukemia and tropical spastic paraparesis/HTLV-1-associated myelopathy. Screening of blood donors for HTLV-1 and HTLV-2 was implemented in Taiwan in February 1996. From February 1996 to December 1998, we investigated the seroprevalence of HTLV-1 in all unpaid blood donors in Taiwan. Of 2,578,238 donors in all 6 blood centers, 1793 (0.06%) were seropositive for HTLV-1, and 605 (0.023%) were indeterminate for HTLV-1. Among these indeterminate donors, 359 (59.3%) were male. The most common HTLV-1-indeterminate pattern by Western blot in our study was GD21 alone (34.6%) followed by p24 alone (7.8%), p53 alone (6.5%), and gp46 + GD21 (6.0%). That GD21 pattern was found in 59.6% of indeterminate results in this study suggested that the majority of nonspecific enzyme immunoassay reactions were probably precipitated by viral envelop glycoprotein GD21.