Evaluation of a new screening assay for HTLV-1 and -2 antibodies for large-scale use.

ABSTRACT

Laboratory testing for Human T-lymphotropic Virus type 1 and 2 (HTLV-1 and -2) infections has become routine in blood transfusion, tissue transplantation and clinical diagnoses in many countries worldwide. Screening is usually based on the detection of antibodies to HTLV-1 and/ or -2. The number of commercially available assays is limited, and among them, ELISA tests based on microtiter format are most commonly used. Recently, the new rHTLV-I/II assay (Abbott Laboratories, Abbott Park, IL) was released; this assay was developed for an automatic large-scale screening platform. This assay was evaluated using pre-characterized serum panels and routine samples from the clinical laboratory. The sensitivity was 100% for HTLV-1 and -2 (99/99 and 42/42, respectively, including one sample that was dually reactive, HTLV-1 + 2). To test assay specificity, panels of blood donor sera, specimens from patients with autoimmune diseases and some viral infections were used. False-reactive samples from previous HTLV diagnoses were also included. With these panels, the specificity was 99.4% (619/623). However, the four false-reactive samples all belonged to the group of samples that were previously considered as false-reactive for HTLV-antibodies. All other samples were negative by the rHTLV-I/II assay, and thus 100% specificity was obtained. The 1,412 samples tested in the clinic by this assay in routine use were all negative (100% specificity). Taken together, the overall specificity was 99.8%. The assay was sensitive, specific and appropriate for the large-scale screening of samples for HTLV-1/2 antibodies.