Do reactions after whole blood donation predict syncope on return donation?

Adverse reactions after whole blood donation reduce the likelihood of a subsequent donation. Still, many donors return to give blood even after experiencing a reaction. Consequently, we evaluated the risk of recurrent syncope among returning donors.

Allogeneic whole blood donors in 2009 who had vasovagal-type reactions including syncope were evaluated for return donation within 12 months and subsequent reactions, based on donation status (novice [first-time] or active [repeat]) or age at index donation.

Syncope after a first whole blood donation significantly reduced the frequency of return donation (18%), compared to either presyncopal symptoms (27%; p < 0.0001) or no reaction (35%; p < 0.0001). Among novice donors who returned to donate, syncope was more likely among donors who had any reaction (0.8%) or syncope (3.5%) at their first donation, compared to donors who had no reaction (0.3%; p < 0.0001). Syncope at a first donation identified only 2% (19 of 1062) of syncopal reactions among returning donors. For active, repeat donors who experienced syncope in 2009, a history of prior reactions had no effect on the likelihood of return donation or recurrent syncope.

Donation experience strongly influences the likelihood of return donation and the risk of subsequent reactions, but a prior reaction after whole blood donation does not reliably predict recurrent syncope among returning donors.