Performance of commercially available serological screening tests for human T-cell lymphotropic virus infection in Brazil.

Serological screening for HTLV-1 is usually performed using enzyme-linked immunosorbent assay, particle agglutination or chemiluminescence assay kits. Due to antigen matrix improvement entailing the use of new HTLV-antigens and changes in the format of HTLV screening tests, as well as newly introduced CLIAs, a systematic evaluation of the accuracy of currently available commercial tests is warranted. We aimed to assess the performance of commercially available screening tests for HTLV diagnosis. A diagnostic accuracy study was conducted on a panel of 397 plasma samples: 200 HTLV-negative, 170 HTLV-positive and 27 indeterminate under Western blotting analysis. WB-indeterminate samples (i.e. those yielding no specific bands for HTLV-1 and/or HTLV-2) were assessed by PCR and results were used to compare agreement among the commercially available ELISA screening tests. For performance analysis, WB-indeterminate samples were excluded, resulting in a final study panel of 370 samples. Three ELISA kits (Murex HTLV-1/2, anti-HTLV-1/2 SYM Solution and Gold ELISA HTLV-1/2) and one CLIA kit (Architect r-HTLV-1/2) were evaluated. All screening tests demonstrated 100% sensitivity. Concerning the HTLV-negative samples, SYM Solution and Gold ELISA kits had specificity values >99.5%, while the Architect r-HTLV-1/2 test presented 98.1% specificity, followed by Murex (92.0%). Regarding the 27 samples with WB-indeterminate results, after PCR confirmation, all ELISA kits showed 100% sensitivity, but low specificity. Accuracy findings were corroborated by Cohen's Kappa, which evidenced slight and fair agreement between PCR analysis and ELISA tests for HTLV diagnosis. Based on the data, we believe that all evaluated tests can be safely used for HTLV-infection screening.