Volume 46, May 2006 TRANSFUSION 703 Blackwell Publishing IncMalden, USATRFTransfusion0041-11322006 American Association of Blood BanksMay 2006465703707Original Article HTLV LOOKBACK AND THE CURRENT HTLV-I AND -II CONFIRMATORY ALGORITHMSTRAMER ET AL. ABBREVIATIONS: ARC = American Red Cross; DVRDL = Department of Viral and Rickettsial Diseases Laboratory; IFA(s) = immunofluorescence assay(s). From the American Red Cross, Biomedical Services Scientific Support Office, Gaithersburg, Maryland; and the American Red Cross Jerome H. Holland Laboratory for Biomedical Sciences, Rockville, Maryland. Address reprint requests to: S.L. Stramer, American Red Cross, Biomedical Services Scientific Support Office, Gaithersburg, MD 20877; e-mail: stramers@usa.redcross.org. Received for publication December 1, 2005; revision received December 21, 2005, and accepted December 24, 2005. doi: 10.1111/j.1537-2995.2006.00788.x TRANSFUSION 2006;46:703-707. TRANSFUSION COMPLICATIONS Effectiveness of human T-lymphotropic virus (HTLV) recipient tracing (lookback) and the current HTLV-I and -II confirmatory algorithm, 1999 to 2004 S.L. Stramer, G.A. Foster, and R.Y. Dodd BACKGROUND: This study reports on the efficacy of an investigational human T-lymphotropic virus (HTLV)-I and -II lookback program in the context of differing confirmatory testing algorithms. STUDY DESIGN AND METHODS: The results of testing approximately 35 million donations for anti-HTLV-I and -II were evaluated for two recent periods reflecting the use of two different confirmatory algorithms. The number of seroconverting donors was established for the entire period, and the results of lookback on their prior donations were investigated. RESULTS: The dual enzyme immunoassay (EIA) strategy was used throughout both study periods and resulted in a 57 to 76 percent reduction in the number of samples requiring confirmatory testing. From May 2000 to February 2002, a total of 9138 samples were repeatedly reactive by the primary screening test; of the concordant EIA-reactive samples, 461 (12%) were confirmed by Western blot, whereas 3083 (79%) were indeterminate. From March 2002 to December 2004, a total of 21,291 samples were repeatedly reactive; of the concordant EIA-reactive samples, 1099 (22%) were confirmed by the State of California’s reference laboratory and only 273 (5%) were equivocal. Overall, 38 or 1 in 921,000 donations were from a seroconverting donor with 32 prior donations within the lookback period. Of those 32, components from only 11 were transfused to recipients who survived; of these, 4 were tested and all were nonreactive for HTLV-I and -II antibodies. CONCLUSION: Use of creative algorithms can increase the efficacy of anti-HTLV-I and -II confirmatory testing and reduce the number of indeterminate results. Currently, lookback for HTLV-I and -II has a very low yield, and its public health benefit is questionable. he AABB’s Transfusion Transmitted Diseases (TTD) committee was charged in 2005 with eval- uating, from a scientific and medical perspective, whether to recommend lookback for recipients of components of prior donations from donors who test positive for the presence of antibodies to the human T- lymphotropic virus (HTLV). Currently, FDA guidance requires product retrieval for in-date components from prior donations from donors who have seroconverted to antibody positivity to HTLV, 1 but in contrast to human immunodeficiency virus and hepatitis C virus (HCV ), there is no requirement to perform recipient tracing and notification for HTLV. This article presents data on the current performance of the HTLV confirmatory algorithm and results of performing HTLV recipient tracing triggered from seroconverting donors from 1999 to 2004; these data were presented to the Transfusion Transmitted Diseases committee for consideration of their charge. Screening of all blood donations for antibodies to HTLV was initiated at the end of 1988; at that time, AABB recommended that recipients of cellular components be notified if transfused with a prior unit from an HTLV- seropositive donor; 2 however, that AABB standard was later deleted. Several studies at the time of the initiation of HTLV screening in the United States supported such a T