Background Recruitment strategies for organ and tissue donors are different, and although some organ donors do eventually become tissue donors, organ donors have significantly different risk factors for communicable diseases than do tissue donors (1,2). Efforts to expand the pool of organ and tissue donors have been a high priority in the transplant community for some time. To increase the supply of human organs for transplantation we must better understand differences in risk factors for major communicable disease between these groups. At present only tissue donors are required by law to be tested by Nucleic Acid Test (NAT) even if this methodology is the most sensitive (2,3). Aim To compare HIV-1 and HCV prevalence among prospective organ and tissue donors from the Western United States screened in our Laboratory. Methods Since September 2004 we tested a total of 20,945 organ and tissue donors from 9 OPOs and 7 Tissue Banks. We tested donors from California, Nevada, Oregon, Washington, New Mexico and Utah. We used:  HCV 3.0 Elisa Test System by Ortho Diagnostics  GS HIV-1/HIV-2 Plus O EIA by Bio-Rad for antibody screening  Procleix HIV-1/HCV Multiplex TMA (GenProbe) for Nucleic Acid Testing (NAT) For this analysis we used most recent data from 2010 and 2011*. *Since December 2011 our laboratory switch to the 3-target NAT TMA test - Ultrio for HIV- 1/HCV/HBV. Results Between January 2010 and October 2011 we tested a total of 2126 organ and 6685 tissue donors. In Tables 1 and 2 we summarized the seroprevalence and NAT prevalence of HIV and HCV among organ and tissue donors. Table 1. Organ vs. Tissue Antibody Reactive Rates a Chi Square test b Fisher Exact test Table 2. Organ vs. Tissue NAT Reactive Rates a Chi Square test b Fisher Exact test Conclusion We found highly statistically significant difference in prevalence of HCV and similar trend for HIV-1 for organ and tissue donors. The prevalence of infections with both viruses is higher among organ donors but only tissue/cadaveric donors have to be tested by NAT. Higher HCV seroprevalence among organ donors suggests that screening protocol for this group will benefit from HCV NAT testing. Despite IVDU exclusion criteria some tissue donors are HCV positive suggesting undisclosed drug use. References 1.Zheng P et al; Reduced effectiveness of standard recruitment for deceased organ donor registration: the need for population-specific recruitment materials. Dig Dis Sci May;56(5): Pruss A et al; Tissue donation and virus safety: more nucleic acid amplification testing is needed. Transpl Infect Dis Oct;12(5): Ellingon K et al; Estimated risk of human immunodeficiency virus and hepatitis C virus infection among potential organ donors from 17 organ procurement organizations in the United States. Am J Transplant Jun;11(6): Organ and Tissue Donors: populations with very different HCV and HIV-1 prevalence – implications for NAT testing Claudia Chinchilla, MB(ASCP), Marcelo Sampaio, Ph.D, Robert Taguibao, CLS, Don J Tanglao, CLS, James Schellenberg, MBA, and Marek Nowicki, PhD Mendez National Institute of Transplantation, Los Angeles, California, United States HCV Ab +HIV-1 Ab +HCV Ab +HIV Ab+ Organ6.5%0.2%5.7%0.3% Tissue2.7%0.2%2.3%0.1% P-values< a b < b b HCV +HIV-1 +HCV +HIV + Organ4.1%0.1%4.2%0.2% Tissue0.9%0%1.0%0% P-values< a b < a b