The donation cycle: a framework for the measurement and analysis of blood donor return behaviour.

The donation cycle represents a new framework for the measurement of blood donor return behaviour. Because it is based on the interval between successive donation attempts, it is more efficient than previously reported methods and the resulting data can be analysed using the statistical techniques for interval data. To illustrate the merits of this quantitative approach to the study of blood donor behaviour, the donation cycle framework is used to analyse the interval between the first and second donation attempts in a random sample (n = 5,183) of type 0, whole blood donors from the Gulf Coast Regional Blood Center. Simple statistical tools such as the log-rank test are employed to describe and to evaluate relative differences in the return behaviour of Rh-negative and Rh-positive donors. The analysis indicates that Rh-negative donors are significantly (p < 0.001) more likely than Rh-positive donors to attempt to donate on a second occasion. Kaplan-Meier estimates of the survival function of these first-time donors reveal marked elevations in the rate of return exactly 52 weeks after the initial donation. The donation cycle paradigm provides transfusion researchers with quantitative tools which are essential for designing statistically efficient, prospective intervention studies. By using the knowledge which such studies could provide, blood banks might be better able to manage donor return behaviour and thereby the safety of the blood supply.