Current value of serologic test for syphilis as a surrogate marker for blood-borne viral infections among blood donors in the United States

Abstract

Background: Serologic screening for syphilis has been justified in part as a surrogate marker for infections caused by other pathogens such as human immunodeficiency virus (HIV). This study assessed the current surrogate value of the test.

Study design and methods: Testing results for blood donors with the American Red Cross Blood Services between January 1, 2006, and December 31, 2007, were analyzed. All donations were tested according to standard procedures for markers of HIV, hepatitis B virus (HBV), hepatitis C virus (HCV), human T-lymphotropic virus (HTLV), syphilis, and other infections. The frequency of window-period (w-p) infections interdicted by syphilis testing was estimated.

Results: There were significantly higher frequencies of HIV, HCV, hepatitis B surface antigen (HBsAg), and HTLV confirmed-positive donations among those with positive syphilis test results, although the sensitivity of syphilis test positivity in these groups was low. Among more than 3 million repeat donors with complete testing through reactive donation confirmation for both syphilis and HIV (anti-HIV and HIV RNA), 225 seroconverted for syphilis but not for anti-HIV or HIV RNA and 83 converted for HIV (anti-HIV or HIV RNA) but not for syphilis, with only 1 who converted for both syphilis and HIV, resulting in an incidence ratio of 150 (95% confidence interval, 21-1080) and a sensitivity of 1.2 percent. No syphilis seroconverters converted for HCV, HBsAg, or anti-HTLV.

Conclusion: Syphilis testing presents no surrogate value for incident HCV, HBV, and HTLV infections and could only remove approximately 1 HIV w-p unit of every 148 million donations.