Deferring blood donors with out-of-range blood pressure: Does it decrease the risk of adverse reactions?

Many blood services defer blood donors with out-of-range blood pressure (BP) readings, but evidence supporting this practice is equivocal. This study assessed the association of pre-donation BP with vasovagal reactions (VVR).

Up until April 2020 ("pre-pandemic period"), donors in Québec (Canada) were deferred if their pre-donation systolic BP was within <90 to >180 mmHg, or if their pre-donation diastolic BP was within <50 to >100 mmHg. Between June 2022 and December 2023 ("late-pandemic period"), BP was measured, but donors with out-of-range readings were no longer deferred. The analysis assessed the association of pre-donation BP with on-site VVRs during the late-pandemic period and compared the rates of on-site VVRs during the pre-pandemic and late-pandemic periods.

189,329 donors made 532,042 donations (mean age = 44.9 years). Overall, 15,825 VVRs occurred, including 14,974 (94.8%) mild VVRs and 15,634 (99.0%) among donors with a normal BP. After adjustment for age, sex, and first-time/repeat status, the odds ratio of VVRs in donors with a low BP was 1.03 (95% confidence interval [CI] = 0.67-1.63) and 0.96 (95% CI = 0.81-1.14) in donors with a high BP, compared to donors with a normal BP. Finally, the VVR rate (95% CI) was 3.0% (2.9%-3.1%) during the pre-pandemic period and 3.1% (3.0%-3.1%) during the late-pandemic period.

There was no association between pre-donation BP and the odds of VVR. The incidence of VVR did not increase after withdrawing the BP deferral. This study provides the most compelling evidence in support of withdrawing BP deferrals in blood donors.