HUMAN T-CELL LEUKEMIA-VIRUS (HTLV-I II) SERODIAGNOSTIC TESTING - DISPARATE RESULTS AMONG A COHORT OF INTRAVENOUS-DRUG-USERS/

Three hundred and forty-six sera collected over-a 2-year period from 1 54 San Francisco IV drug users were subjected to HTLV-I/II RIPA, Weste rn blot (WB), Du Pont ELISA, and p24 radioimmunoassay (RIA). Tests wer e performed at separate sites and code not broken until study end. RIP A-positive and -negative controls consisted of Japanese adult T cell l eukemia patients, healthy blood donors, and non-IV drug-using HIV-posi tive men. RIPA identified HTLV-I/II-positive sera not identified by th e other tests. Positive RIPAs were noted in 43% of negative ELISAs (n = 279), 34% of negative WBs (n = 243), and 40% of negative RIAs (n = 2 70). Seventy-two sera were negative by all 3 assays, but were RIPA pos itive. All sera positive by RIA (n = 76) and WB (n = 67), and 66 of 67 by ELISA, were positive by RIPA. Thirty-five of 36 indeterminate WBs were RIPA positive. Seven samples indeterminate by RIPA were negative by WB and RIA; one of seven was positive by ELISA. In all instances, s amples negative by RIPA (n = 154) were ELISA, p24 RIA, and WB negative or indeterminate. We conclude that when studying HTLV-I/II-endemic co horts, screening ELISA or RIA followed by confirmatory WB or RIPA only of seropositive samples may result in a substantial number of undetec ted cases. Additional studies focusing on performance characteristics of serodiagnostic tests are needed to ensure accurate inferences are m ade in assessing HTLV-I/II prevalence rates among high-risk groups. Th e RIPA may be a uniquely sensitive assay to detect HTLV-I/II gene-enco ded products.