A brief report published in Transfusion uses data from the U.S. Transfusion-Transmissible Infections Monitoring System (TTIMS), which represents 60 percent of the country’s blood supply, to explore transfusion-transmissible coinfections and, “the prevalence of blood donations positive for two or more transfusion-transmissible infections (TTIs), or coinfections (past or present). The investigators of this study also, “describe the demographic characteristics of these unique donors, and evaluate the relationship of the various combinations of TTIs.”
The study of transfusion-transmissible coinfections included TTIMS data from October 2020 to September 2023 as only, “donors of allogeneic (including COVID-19 convalescent plasma) and directed donations with valid test results for monitored infectious disease markers (HIV, HBV, HCV, and syphilis) were included in the analysis.” The authors explained that they defined coinfections as, “donations with multiple positive markers identifying the donor as infected with any combination of HIV, HBV, HCV, or syphilis infection in the same donation.” The dataset for the analysis featured 21,962,111 donations from 6,846,036 donors over the three-year span.
The analysis of transfusion-transmissible coinfections discovered a, “total of 10,516 donations from TTI-infected donors (overall prevalence of 478.8 per million donations (pmd)) includ[ing] 439 HIV consensus positive (CP) (20.0 pmd), 1,346 HBV CP (61.3 pmd), 2,105 HCV CP (95.8 pmd), and 6,842 syphilis CP (311.5 pmd) donations. While the vast majority were infections with a single agent (N=10,304), there were 212 CP coinfections, yielding a coinfection prevalence of 9.7 pmd (95 percent CI: 8.4, 11.0).”
The authors of the transfusion-transmissible coinfections study further explained that, “[t]he proportion of donations from coinfected donors for any TTI-positive combination was 212 of 10,516 (2 percent) TTI-positive donations. Coinfection prevalence by TTI combination ranged from 0.3 pmd (95 percent CI: 0.1, 0.7) for HIV CP and HCV CP to 4.3 pmd (95 percent CI: 3.5, 5.3) for HIV CP and syphilis CP. Of note, there were four donors having infections with three agents, all involving HIV and syphilis (CP or active syphilis infection (ASI)) in combination with either HBV or HCV for a donation frequency of 0.2 pmd (95 percent CI: 0.05, 0.5). The most common coinfections were in combination with syphilis, whether CP or ASI. Of the 439 HIV CP in the three-year period, 21.6 percent were syphilis CP, illustrating the high degree of similarity in the epidemiology of infection with these two agents.”
Donors with coinfections were predominantly male (84 percent) between the ages of 25-39 (31.1 percent) or 40-54 (34.9 percent). Additionally, 35.9 percent identified as white, and 34.9 percent were black. Also of note, 80.2 percent were first time donors and 79.3 percent resided in the southern portion of the U.S. The investigators also found that, “[w]hen comparing the coinfection group with the single TTI group, all were significantly different across strata (p=.03 for repeat donor status, p<.0001 for the rest), except for age group (p=.5), for which both groups had similar proportions. When comparing the coinfection group with the non-TTI group, all were significantly different across strata (p<.0001).”
The transfusion-transmissible coinfections study analysis indicated that, “[a]ll individual TTIs were significantly associated with one another. The lowest magnitude of association was between HBV CP and ASI; a donor positive for HBV CP was 23 (95 percent CI: 13, 41) times more likely to also be positive for an ASI compared with a donor not HBV CP. The highest magnitude of association was between HIV CP and ASI; an HIV CP donor was 395 (95 percent CI: 298, 524) times more likely to also be positive for an ASI compared with a donor not defined as an HIV CP. Even though HIV CP and syphilis CP was the most frequent coinfection, the odds of an ASI donor also being an HIV CP was higher compared with the odds of a syphilis CP donor being also HIV CP, although in both analyses, the relationships between HIV CP and syphilis (whether CP or ASI) were similar. Syphilis CP was still highly associated with HIV CP with an odds ratio of 282 (95 percent CI: 224, 354).”
The authors of the transfusion-transmissible coinfections study concluded that, “[s]imilar to the general population infected with these agents, coinfections are relatively uncommon (approximately 2 percent) among infected (past or present) blood donors in the U.S. The current study, among blood donors, indicates that HIV, HBV, HCV, and syphilis are all associated with each other, likely due to shared routes of transmission. These relationships between TTIs should be considered when evaluating blood safety and current interventions.”
Citation: Conti, G., Notari, E.P., Dodd, R.Y., et al. “Transfusion-transmissible coinfections among U.S. blood donors.” Transfusion. 2024.