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Transfusion. 2008 Sep;48(9):1799-808. doi: 10.1111/j.1537-2995.2008.01745.x. Epub 2008 May 14.

Faint and prefaint reactions in whole-blood donors: an analysis of predonation measurements and their predictive value.

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  • 1United Blood Services, and Blood Systems, Scottsdale, Arizona; and Blood Systems Research Institute, San Francisco, California, USA.



A small proportion of blood donors have adverse reactions. The purpose of this study was to determine predictors of faint and significant hypotensive reactions that could serve as targets for interventions to reduce reactions, thus improving the blood donation experience for those at higher risk of reactions and reducing the risk of serious adverse events.


The records of 422,231 allogeneic whole-blood donations from a 9-month period were assessed for adverse reactions. Incidents related to needle insertion, such as hematoma, were excluded. Demographic, biometric, and clinical measurements were collected. Reactions were analyzed by multivariate logistic regression analysis comparing donors with any adverse reaction to donors without reactions and by stratified rates according to reaction severity.


The overall reaction prevalence was 1.43 percent. Of the reactions, 63, 29, and 8 percent were classified as mild, moderate, and severe, respectively. Markers of reactions were age, sex, race, blood volume, blood pressure, pulse, and body mass index. Compared to donors without reactions, the strongest predictor of a reaction was a donor's blood volume of less than 3500 mL (odds ratio [OR], 2.9; 95% confidence interval [CI], 2.57-3.23). Age and first-time status were also associated with a significantly higher risk of reaction with 17- to 18-year-olds (OR, 2.8; 95% CI, 2.59-2.98) and 19- to 24-year-olds (OR, 2.39; 95% CI, 2.23-2.56) at higher risk compared to 25- to 65-year-olds and first-time donors at higher risk compared to repeat donors (OR, 2.2; 95% CI, 2.07-2.33).


The results of this study are helpful in identifying donors at risk for adverse reactions and in understanding the contributors to reactions. Donor blood volume was an unexpectedly strong predictor of reaction. Potential interventions to reduce the frequency of reaction are discussed.

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