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rather than younger female apheresis donors with no association observed in male apheresis donors. Donor characteristics that are unobservable without further questioning or assessment Once observable donor characteristics are taken into account, other factors emerge as being predictive of VVRs. These range from factors that can be assessed as part of a routine blood donation (e.g., pre-donation blood pressure, pulse; Ogata et al. 1980; Kasprisin et al. 1992; Takanashi et al. 2012) to lifestyle factors (e.g., prior night sleep duration [Takanashi et al. 2012], prior food [Takanashi et al. 2012], and/or caffeine intake [Kasprisin et al. 1992; Meade et al. 1996)]). Further, donor characteristics, such as a history of fainting (Meade et al. 1996), along with underlying or situationally induced (psychological) states (e.g., anxiety [Ditto and France 2006b], anticipated anxiety [Olatunji et al. 2010; Viar et al. 2010], fear of blood and injury [Meade et al. 1996; Labus et al. 2000; Ditto et al. 2012], fear of blood draw [France et al. 2013], perceived blood loss [Ditto et al. 2012], pain [Meade et al. 1996], anticipated pain [Olatunji et al. 2010], and anticipated disgust [Olatunji et al. 2010; Viar et al. 2010]) have also been associated with perceived VVR type symptoms. As with the observable donor characteristics analyses, many of the analyses exploring the predictive value of these unobservable characteristics have taken a multivariate approach. For example, Takanashi et al. (2012) compared the records of 4,924 Japanese donors who had experienced a VVR to a control group of 43,948 donors with no donation-related complications. For both male and female donors, being a first-time donor, having a pre-donation pulse of greater or equal to 90 beats per minute, a diastolic blood pressure of This article is protected by copyright. All rights reserved. 7 equal to or below 70 mmHg, a sleep duration of 6 hours or less (compared to eight hours or more) and having not eaten a meal in the last four hours were all independently significantly associated with a greater risk of a VVR after adjusting for age, sex, BMI, pulse and systolic blood pressure. When considering psychological states, anticipatory anxiety or fear of aspects of the phlebotomy process appear to have a more consistent association with VVR, in comparison to other affective reactions that have been examined (e.g., disgust) (Olatunji et al. 2010; Vossbeck-Elsebusch and Gerlach 2012). While the studies focused on psychological states are smaller in scope and fewer in number in comparison to the demographic analyses, anticipatory anxiety and/or fear are consistent predictors of experiencing vasovagal sensations (Meade et al. 1996; Labus et al. 2000; Ditto and France 2006b; Olatunji et al. 2010; Ditto et al. 2012; Gilchrist and Ditto 2015). While theoretically anxiety may more accurately reflect the uncertainty that donors feel around whether the outcome of donating will be good or bad (Chell et al. 2016), analyses using a single question to assess fear of having blood taken show good predictive ability in identifying those most at risk of a VVR. France and colleagues (2013) asked 1715 high school students aged 17-18 years waiting to donate blood to self-report their fear of the blood draw on a simple 1 (no fear) to 4 scale and then tracked their subsequent donation to assess whether they experienced a VVR or not. The VVR rate of a control sample of 1692 donors who were not asked the fear question was also obtained. Initial analyses indicated that asking the fear question did not cause an increase in the rate of VVRs, as the rate of VVR did not differ between the question and control group for either firsttime or more experienced donors. Further, when fear of the blood draw was considered in a This article is protected by copyright. All rights reserved. 8 multivariate analysis alongside other identified predictors of VVR (e.g., age, gender, donor status, body mass, estimated blood volume, systolic blood pressure, diastolic blood pressure, pulse rate), only self-reported fear of the blood draw, estimated blood volume, and gender of the donor emerged as significant predictors of VVR. The rate of VVR was higher among those with greater fear and lower estimated blood volume. In this analysis, contrary to other studies, once fear and estimated blood volume were controlled for, male donors were at a greater risk of VVR than female donors. Contextual features Alongside the characteristics that the donor brings to the donation setting, there are contextual features that may influence a donor’s risk of experiencing a VVR. The association of these with donors’ experiences of VVR has been considered in a small number of analyses. Ogata et al. (1980) analysed the records of 10,547 Japanese donors and found that VVRs were more frequent in the spring and least common in the summer. Further, reactions were more common

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