Higher rates of laboratory‐confirmed cases of syphilis in Western Canadian blood donors compared with Eastern Canadian blood donors following a period of societal re‐opening.

Background and Objectives: There is a growing infectious syphilis outbreak in Western Canada. Although blood donors are screened for syphilis risks, some blood donors will still be confirmed test‐positive for syphilis. This study compares the characteristics of confirmed test‐positive syphilis donations in both Western Canada and Eastern Canada, November 2022–August 2023. Materials and Methods: Donors were defined as Western or Eastern Canadian. Blood donations were tested for syphilis using the PK‐TP assay (Beckman Coulter PK7300 Automated Microplate System). Confirmatory Treponema pallidum particle agglutination (TPPA) and rapid plasma reagin (RPR) assays were performed by one of two reference laboratories. An RPR titre ≥1:8 was used as a proxy for possible infectious syphilis. Results: Rates of laboratory‐confirmed syphilis were higher in Western (n = 43, 13.4/100,000 donations) versus Eastern donors (n = 19, 4.7/100,000 donations; Fisher's exact test, two‐sided, p ≤ 0.0001). Most syphilis confirmations were in first‐time donors (Western Canada n = 31/43, 72.1%, Eastern Canada 12/19, 63.2%). Conclusion: Although rates of laboratory‐confirmed syphilis were higher in Western versus Eastern donors, Western donors did not have higher rates of infectious syphilis. Further studies might assess whether donors with laboratory‐confirmed syphilis understood pre‐donation screening questions or were completely unaware of a past infection. [ABSTRACT FROM AUTHOR]