(P-BC-53) Serologic characterization of Blood Donors with reactive Anti-Treponema Pallidum results in an Upper-Middle-Income Country Hospital Blood Bank

Colombian regulations require a treponemal test for Syphilis screening of blood donors (Total antibodies for anti-Treponema pallidum (Tp)). However, Tp seroreactivity in blood donors represents a significant challenge for blood banks (BB), especially in Upper-Middle-Income Countries (UMIC) where infectious disease prevalence and public health policies can influence transfusion safety. Previous studies in Latin America have shown that syphilis seropositivity in blood donors can reflect epidemiological trends in the general population, affecting available blood reserves. This study aimed to characterize the serological profile of Syphilis reactive blood donors from a Colombian hospital BB.


 

Study

Design/Methods:

Following Colombian regulations, we tested 77,326 blood donors for seven serological markers to mitigate the transmission of infections through transfusion (ITT).  Anti-Tp by Chemiluminescence Microparticle Immunoassay  (CMIA) was included from 01/01/2018 until 12/31/2023. In addition, molecular screening by multiplex Nucleic Acid Test (NAT) was performed in all donors in mini pools of 6 donors for HBV, HIV, and HCV since 05/03/2022. Subsequently, reactive donors for anti-Tp  by CMIA were selected for further testing using Rapid Plasma Reagin (RPR test or RPR titer) and fluorescent treponemal antibody absorption (FTA-ABS).

Results/Findings:

The reactive rate for anti-Tp by CMIA was 0.92% (709 donors in total). Men represented 52.3% of reactive blood donors, 93.1% were whole blood donors, and 10.9% were repeat blood donors. The average age of reactive donors was 42.47 (+ 13.37) years. The agreement reactive between anti-Tp by CMIA and RPR Test reactive plus FTA-ABS positive was 27.43% (152 donors deferred permanently for active state infection of Syphilis). On the other hand, 72.57% of volunteer blood donors were FTA-ABS positive and negative for RPR, suggesting past exposure with no active infection. Additionally, 0.11% (85/77326) of seroreactive blood donors to normative screening had two or more reactive tests, of which 28.23% (24/85) had reactive screening for syphilis. 3.38% (24/709) syphilis reactive donors had more than two reactive screening tests: HIV plus Syphilis: 1.27%; HIV + HBV + Syphilis: 0.85%; HCV plus Syphilis: 0.71%; Chagas Disease plus Syphilis: 0.42%.

Conclusions: We observed that 72.57% of reactive donors are noninfectious and therefore an acceptance or reentry program could be implemented to reduce the impact of discarding these donations. The present study will allow us to review the current screening and confirmatory algorithm for syphilis in Colombia.