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in underlying mechanisms leading to LOC. It is possible that period-specific interventions may be useful in reducing fainting reactions that might lead to injury. During Period 1 (registration and screening), the donor is walking or sitting. The data suggest the risk factors to be mainly demographic characteristics of donors; young age and first-time status and the stimuli for fainting may be primarily psychological. During Period 1, the donors’ blood volume does not change and the only procedures experienced by the donors are the interview, the vital signs and a finger stick to determine haemoglobin level. During phlebotomy (Period 2), the strong association of incomplete donation status with LOC may reflect the fact that the reaction prompted the discontinuation of the donation process. The most important donor factor associated with LOC is small EBV. This is consistent with the fact that the majority of LOC events during this period occur at the time of needle removal (Fig. 1), suggesting relative hypovolemia as a contributing factor. In addition, first-time donor status and young age are also significant predictors of LOC. Donors who faint in the recumbent position have lower potential for injury. At the beginning of Period 3A, the donor’s posture changes from recumbent to upright. The time course shows two peaks of LOC events at 5 and 9 min after the time of needle removal. We believe that the peak at T = 5 represents fainting occurring at the time the donor leaves the donor chair and that at T = 9 occurs as the donor is ambulating in the refreshment area. Young age, small EBV and first-time donor status are the main factors associated with fainting during this period. Of note, donors with a Predonation pulse >90 beats per minute and donors older than 65 years of age were also at significantly higher risk of fainting. Events during this period show the highest rate ⁄ donation of donor injuries and need for OMC. In Period 3A, the rate of injury and OMC per 100 fainting events was higher than in Period 2. Ten per cent of fainting episodes associated with whole blood donations occurred off-site (Period 3B). Low EBV, female gender, younger age and first-time donor status are the characteristics associated with higher risk. This group has a higher ratio of injury risk ⁄ LOC event possibly due to the fact that LOC occurs outside the area of staff observation. It is also possible that the more serious events requiring OMC are disproportionately reported to the blood centre. Period 2, when the donor is recumbent, has a lower male and female rate of injury per LOC reaction and a lower rate Table 3 Injury and OMC, by gender, associated with fainting reactions Period C, outside medical care a Rate is expressed as number of events per 1000 registration in Period 1 and per 1000 donations in Periods 2 and 3. 8 M. Bravo et al. 2011 The Author(s) Vox Sanguinis 2011 International Society of Blood Transfusion, Vox Sanguinis (2011) of injury per donation than Period 3A and 3B. The potential for injury is likely to be lower if the donor reacts while recumbent. Period 3A shows a higher ratio of rate ⁄ donation for injury and OMC compared to other periods which may be attributed to the upright posture at this stage in the donation process. An interesting finding of this study is that the risk of LOC reaction was lower in Periods 2, 3A and 3B for donations that occurred at fixed sites vs. donations occurring on buses or at mobile, inside set-ups (Table 1 and Fig. 1). While it is more likely that older and repeat donors attend fixed site donation clinics leading to lower reaction rates, this lower risk was apparent in the multivariable analysis that controlled for these characteristics as well as in the rate analysis. A point of future investigation may be the donor’s position during donation. The elevation of the donor’s head, pelvis, knees and feet in relation to the position of the donor’s heart varies with the chairs or beds used for donation and there can be different impacts on donor blood volume related to body position. Body position during donation may influence the delayed reaction rate. There was wide and statistically significant variation in the rate of fainting reactions among the 15 UBS blood centres (Data not shown). In the multivariable analyses, the blood centre was a consistent risk factor, with some centres having low while others had high risks for LOC reaction. Results showed a significantly decreased risk of reaction across various centres compared to the reference centre in the logistic regression analyses (the centre with the largest number of donations). In previous studies, rates of donor adverse events varied significantly among blood centres that use standardized training, procedures and classification systems [2,3]. The cause of this variation is unknown and will continue to present a challenge in interpreting data as blood collection facilities participate in donor

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