To the Editor Dr Caram-Deelder and colleagues1 reported an association between receipt of a red blood cell transfusion from an ever-pregnant female blood donor and increased mortality among male recipients. However, the association was weak (hazard ratio, 1.13 [95% CI, 1.01-1.26]; P = .03), and such weak associations in observational studies can easily be attributable to chance.2 The hazard ratio should also be viewed skeptically given a number of statistical problems in the analyses.
Pocock SJ, Alonso AC. Ever-Pregnant Female Blood Donors and Mortality Risk in Male Recipients. JAMA. 2018;319(10):1048. doi:10.1001/jama.2017.21868
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