Predictive ability of sequential surveys in determining donor loss from increasingly stringent variant...

Predonation screening questions about travel increase the safety of the blood supply from diseases such as variant Creutzfeldt-Jakob disease (vCJD) and malaria. This study examines the ability of sequential surveys to predict actual travel deferrals and the operational validity of travel questions.

To assess donor travel histories before implementing key deferral policies, two donor surveys were carried out at Canadian Blood Services collection sites in February 1999 (8026 donors) and March 2001 (13,623 donors). In-person interviews were carried out with 1530 donors to assess the operational validity of the short travel question. Time-series analysis was used to determine whether there was a change in deferrals when deferral policies were implemented. Predicted donor loss estimates based on survey results were compared with actual deferrals.

Deferrals increased significantly (p < 0.05) when vCJD deferral policies were implemented in October 1999 and September 2001, but not in October 2000. Survey data accurately predicted deferrals 6 months after implementation from the initial policy (2.51% predicted vs. 2.51% actual), but there were fewer deferrals than predicted for the second (2.89% predicted vs. 2.26% actual, p < 0.01) and third deferral policies (3.10% predicted vs. 1.89% actual, p < 0.01). There was 96 percent agreement between donor responses to a short screening question and a detailed travel history.

The initial survey accurately predicted the actual donor deferral rate, but the deferral rate was less than predicted for subsequent, more stringent donor deferral policies. Donors answered a short travel question suitable for donor screening similarly to a very detailed travel history.