Currently, in almost every country in the world, all donated blood is systematically screened for syphilis. However, there is an ongoing debate on whether this universal screening is cost-effective. This debate is fuelled by the low number of reported cases of transfusion-transmitted syphilis, combined with a widespread belief that the syphilis-causing bacterium Treponema pallidum (T. pallidum) cannot survive in blood that is stored cold (or at room temperature) for over 72 hours. However, this claim is not supported by a systematic review of the literature. Therefore, we conducted a systematic review to investigate whether syphilis can be transmitted via transfusion after blood products have been stored either at cold or room temperatures for different periods of time.
We searched 5 online databases and retrieved a total of 10 eligible studies, including 9 experimental animal studies and 1 observational human study.
Meta-analyses showed that storing blood that has been artificially infected with T. pallidum at refrigerated temperature for more than 72 hours before injecting it into rats or rabbits, significantly decreases the number of animals that subsequently developed syphilis, compared with storing the blood for less than 72 hours before injection. However, even if the infectivity of T. pallidum-spiked blood may decrease after 72 hours of cold storage, the possibility for the transmission of syphilis may remain in existence for up to 7 days of cold storage in some studies.
All included studies had very small sample sizes. Conclusions are therefore hindered both by a lack of sufficiently powered studies and a lack of studies in humans. Indeed, it is very unclear whether findings that have been obtained under very artificial circumstances in animals can be translated to a real-life setting.
Based on the currently available evidence, it thus remains highly uncertain whether prolonged storage can indeed be relied upon to eradicate the risk of transfusion-transmitted syphilis.
The review has been published in Vox Sanguinis.