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.

Although nucleic acid amplification testing of minipools of blood donations prevented hundreds of cases of West Nile virus infection in 2003, it failed to detect units with a low level of viremia, some of which were antibody-negative and infectious. These data support the use of targeted nucleic acid amplification testing of individual donations in high-prevalence regions, a strategy that was implemented successfully in 2004.

Low EBV, youth, and first-time donor status are major risk factors for IRs and DRs. Women are more likely than men to report DRs. Delayed and off-site reactions lead to potentially preventable morbidity. Understanding the physiologic basis of DRs may lead to the development of appropriate interventions to reduce their likelihood.

BACKGROUND  Whole blood (WB) donation encompasses several periods during which some donors faint. Identification of factors associated with fainting during each period should guide intervention strategies. Reducing faint reactions may reduce donor injuries and disability. METHODS  Blood donation was divided into three periods: Period 1 - registration; Period 2 - phlebotomy; and Period 3 - post-phlebotomy. Period 3 consists of two sub-periods (3A - on-site and 3B - off-site). For each Period, stratified rates of fainting in relation to various donor and donation characteristics were calculated and multivariable logistic regression analyses to identify factors associated with fainting were conducted. Donor injuries in each period were also analysed. RESULTS  Of the 956 766 donors registered in 2007, 554 534 (58%) donated WB. There were 43 fainting episodes and two injuries in Period 1 and 1520 faints and 73 injuries in Periods 2 and 3. Regression analyses showed that youth and donor first-time status are associated with fainting in all periods; but most significantly in Period 1. Small estimated blood volume is notably not a factor in Period 1 but is significant in Periods 2 and 3. The highest injury rate is seen in Period 3A (0·07 and 0·09/1000 donations) for male and female donors, respectively. CONCLUSIONS  Variability in factors associated with fainting across defined periods of the donation process suggest differing underlying mechanisms and the possibility that interventions for the reactions most associated with injury during each time period can be designed. The highest rate of injury per donation occurred in ambulating donors.

Donor deferral rates in regional blood centers vary from 5 to 24 per cent, reducing by more than 1,250,000 the number of units of volunteer blood available for transfusion in the nation each year. Those criteria for donor deferral which are intended to exclude donors likely to suffer a "donor reaction" are based partially on untested hypotheses and tradition. In a six-month prospective study, we adopted more liberal criteria for donor acceptance. During this period, donor reaction rates did not increase, and the deferral rate fell from 10 to 7 per cent. Our findings suggest that less restrictive criteria can be used for donor selection without compromising donor safety. If all blood centers reduced their deferral rates to 7 per cent, the nation's blood supply would be increased by more than 500,000 units annually.

The interventions to reduce vasovagal reactions in whole blood donors were effective. Future efforts to reduce reactions in blood donors can build on the strengths and avoid the weaknesses identified while conducting and analyzing the data from this study.

Vasovagal syncope (VVS) is a consistent, but infrequent (0.1%-0.3%) complication of volunteer, whole blood donation. Given the large number of blood donations, a significant number of donors is involved. Syncope occasionally leads to injury. Recent rigorous data collection and analysis have led to the association of a small number of donor and donation factors with the risk of syncope. An analysis of the time course of syncope reactions among approximately 500,000 whole blood donors suggests that there are three distinct periods of risk for vasovagal reactions before, during, and after phlebotomy. This review examines the physiologic mechanisms that contribute to these periods of increased risk including the direct effects of removal of approximately 500 mL of whole blood, the psychological stress of instrumentation and giving blood (i.e., fear of needles, pain, and the sight of blood), and the orthostatic effects superimposed on a hypovolemic state after the donation. Specifically, we describe interventions that have been useful in controlling VVS in patients with fainting syndromes and we examine the potential of these interventions in the blood donation context, based on the physiologic principles involved. Finally, we propose an intervention (dietary replacement of salt lost with blood donation) that has not been applied in transfusion medicine previously but which has the potential to reduce risk.

These data corroborate the fact that the rate of detection of truly contaminated PLT apheresis products in the United States is approximately 1 in 5000 (0.02%); this is lower than the 0.03 to 0.05 percent rates that were generally quoted in the literature before the implementation of prospective bacterial culturing programs.