Analysis of a questionnaire on adverse reactions to blood donation in Japan.

In 2007, the Japanese Red Cross Blood Center performed a large-scale questionnaire study of post-donation adverse reactions. The questionnaire was distributed to 98,389 donors, and the answers were returned by 55,231 (56.1%). In total, 2,877 (5.2%) complained of an adverse reaction. Assuming that there were no adverse reactions for the 46,150 donors who did not reply, the rate of adverse reaction can be speculated to be 2.8%. Our study strongly suggests that blood centers have long underestimated the risks of vaso-vagal reactions. Taking at least 6h of careful rest after donation would be a helpful counter measure.