Does cold storage of blood before transfusion prevent the transmission of syphilis? A systematic review and meta-analysis.

Abstract

Although screening of donated blood for syphilis is almost universally applied, its cost-effectiveness is questioned because of the low prevalence of transfusion-transmitted syphilis and a widespread belief that the syphilis-causing bacterium Treponema pallidum is very vulnerable to cold storage. Since the latter claim is not yet supported by a systematic review, we investigated whether syphilis can be transmitted via transfusion following prolonged (cold or room temperature) storage of blood products. MEDLINE, PMC and NCBI bookshelf (PubMed interface), Cochrane Library, Embase, Web of Science and CINAHL were searched up to 17 January 2023. Nine experimental animal studies and one observational human study were included. Meta-analysis showed that storing artificially infected human (six studies; risk ratio [RR] = 0.37, 95% confidence interval [CI]: 0.22-0.64, p = 0.0003) or rabbit (two studies; RR = 0.08, 95% CI: 0.01 to 0.55, p = 0.01) blood for more than 72 h before intratesticular injection significantly decreased the number of recipient animals that develop syphilis. Nonetheless, the possibility of syphilis transmission remained for up to 7 days. Differences could not be found for rabbit plasma (p = 0.60) or naturally infected rabbit blood (p = 0.28). There was limited evidence from one study in favour of the storage of artificially infected human platelets for over 72 h at cold temperatures (RR = 0.13, 95% CI: 0.03-0.52, p = 0.004) but not at room temperature (p = 0.12). Even though the infectivity of T. pallidum-spiked blood may decrease after 72 h of cold storage, the possibility for transfusion-transmitted syphilis may remain for several days after. The evidence is very uncertain, and conclusions are hindered by a lack of sufficiently powered studies and studies in humans. In addition, T. pallidum concentrations used in animal studies may be unrealistically high.