Comparison of Syphilis Screening Tests in Deceased Organ Donors

Abstract

Introduction: Current US policy requires screening of all organ donors for syphilis infection. False positive results may occur. Methods: All deceased organ donors who were evaluated by one US Organ Procurement Organization (OPO) (Gift of Hope) from 2000-2011 with a reactive RPR (+ RPR) result (Macro-Vue RPR, BD, Franklin Lakes, NJ) were retrospectively tested with 3 treponemal tests: Fluorescent Treponemal Antibody absorption (FTA-ABS, Scimedx, Denville, NJ), a microhemagglutination test (Olympus PK-TP System, Fujirebio, Tokyo, Japan), and a chemiluminescent assay (LIAISON Treponema Assay, DiaSorin, Stillwater, MN). Outcomes and management of recipients was not assessed. Results: Thirty donors had a reactive RPR out of 3,268 (0.9%) potential organ donors evaluated for syphilis from 2000-2011; the mean age of donors with a + RPR was 51 years and 77% were male. Fourteen (47%) of the RPR + donors were found to be false positive based on confirmatory FTA-ABS (Table 1). Only 16 (53%) of the donors had a total of 47 organs recovered for transplantation. The PK-TP and LIAISON tests were 100% concordant with each other but would have given false negative results in 2 donors. The sensitivity, specificity and positive predictive value of the assays are shown in table 2.Conclusions: RPR screening yields a significant number of false positive results in organ donors. Use of alternative tests or the routine use of confirmatory assays may reduce the frequency of false positive results. Based on this single OPO experience, there is also significant variability in the use of RPR reactive donors. Future studies should assess the impact of confirmatory testing or testing strategies with a lower false positive rate on donor utilization.