Lessons from the INTERVAL study – Authors' reply

The INTERVAL study randomly assigned 45 263 whole-blood donors to different intervals between donations to assess the effect of varying the frequency of donation on donor health and blood supply. Reducing the inter-donation intervals used in the UK to those used in blood services in the USA or western Europe led to a substantial increase in the amount of blood collected over the 2-year study period. For instance, reducing the inter-donation interval from 12 weeks to 8 weeks in men led to an increase in blood supply of 33% (an average of 1·7 units per donor). No significant differences were observed in quality of life, physical activity, or cognitive function across randomised groups. However, more frequent donation resulted in more donation related symptoms (eg, tiredness), lower mean haemoglobin and ferritin concentrations, and more deferrals for low haemoglobin. Katja van den Hurk and colleagues noted that ...