TRANSFUSION COMPLICATIONS Clinical specificity and sensitivity of a blood screening assay for detection of HIV-1 and HCV RNA Janet Vargo, Katie Smith, Caroline Knott, Songbai Wang, Chyang Fang, Sherrol McDonough, Cristina Giachetti, Sally Caglioti, Richard Gammon, Denise Gilbert, J. Brooks Jackson, William Richards, Susan Stramer, and Larry Mimms BACKGROUND: An HIV-1 and HCV NAT blood screening assay (Procleix HIV-1/HCV, Gen-Probe, Inc.) simultaneously detecting HIV-1 and HCV RNA) has been implemented. Donor plasma samples reactive in the Procleix HIV-1/HCV assay are tested with the HIV-1 and HCV discriminatory assays to resolve whether HIV-1 RNA, HCV RNA, or both are present. STUDY DESIGN AND METHODS: To determine the specificity of the Procleix HIV-1/HCV assay, data were analyzed for samples from 192,288 donations, tested in 16-member pools. To determine sensitivity, data were analyzed for 2014 commercial samples known to con- tain HIV-1, HCV, or both, as well as 10 HIV-1 and 10 HCV commercial seroconversion panels. RESULTS: The specificity of the Procleix HIV-1/HCV assay was 99.7 percent. The HIV-1 and HCV discrimi- natory assays showed similar specificity. The sensitivity of the Procleix HIV-1/ HCV assay was 99.9, 99.6, and 100 percent, respectively, for samples containing HIV-1, HCV, or both. The Procleix discriminatory assays were comparably sensitive. The Procleix discriminatory as- says detected all tested samples of known HIV-1 sub- type or HCV genotype. Procleix HIV-1/HCV testing of seroconversion panels showed that the median times to a positive reaction for HIV-1 and HCV were reduced by 3 and 25 days, respectively, compared to serologic tests. CONCLUSION: These studies support the use of the Procleix HIV-1/HCV assay for routine blood donor screening. A n HIV-1 and HCV assay (Procleix; Gen-Probe, Inc. San Diego, CA) was developed in response to requirements for a highly sensitive, NAT blood screening technology that could reduce the window period between infection and the detectabil- ity of infection by standard serologic tests and therefore increase the chance of interdicting infectious donations. The Committee for Proprietary Medicinal Products of the European Union requires the use of NAT to screen blood and plasma donations. 1 Since 1999, considerable clinical experience in blood banks with the Procleix HIV-1/HCV assay has been obtained in the United States. 2-4 The Procleix assay comprises three processes in the same test tube: sample preparation (target capture), tran- scription-mediated amplification (TMA) of HIV-1 and HCV target RNA sequences, and detection of amplifica- tion products (amplicons) with a hybridization protec- tion assay (HPA). The assay method has been described in detail. 5,6 During sample preparation, viral RNA is isolated from plasma by target capture. Oligonucleotides (“cap- ture oligonucleotides”) homologous to highly conserved regions of the HIV-1 and HCV genomes are hybridized to ABBREVIATIONS: HPA = hybridization protection assay; NGI = National Genetics Institute; p24Ag = p24 antigen; TMA = transcription-mediated amplification; TP = true positive. From Gen-Probe Incorporated, San Diego, California; Chiron Corporation, Emeryville, California; Blood Systems Laborato- ries, Tempe, Arizona; Association of Independent Blood Cen- ters, Lakeland, Florida; Florida Blood Services, St. Petersburg, Florida; Johns Hopkins University, Baltimore, Maryland; Blood Center of Southeastern Wisconsin, Milwaukee, Wisconsin; and American Red Cross, Gaithersburg, Maryland. Address reprint requests to: Janet M. Vargo, PhD, Clinical Affairs, Gen-Probe Incorporated, 10210 Genetic Center Drive, San Diego, CA 92121; e-mail: janetv@gen-probe.com. Received for publication August 24, 2001; revision re- ceived March 5, 2002, and accepted March 5, 2002. TRANSFUSION 2002;42:876-885. 876 TRANSFUSION Volume 42, July 2002