Ethnicity, length of time on the register and sex predict donor availability at the confirmatory typing stage.

Despite over 20 million unrelated donors being listed worldwide, donor attrition at the confirmatory typing (CT) stage of donor acquisition is a key source of delay. Anthony Nolan undertook a study of CT requests from 2010 to 2011 to identify factors associated with attrition. Of 7541 CT requests, 38.2% were cancelled for donor reasons. Of these, 19.4% were personal, 34.1% medical, 36% no contact, 7.9% emigrated and 2.6% others. African (odds ratio (OR) 2.78, P<0.001), African-Caribbean (OR 3.07, P<0.001), Asian (OR 2.65, P<0.001), Jewish (OR 1.54, P=0.009) and Mediterranean (OR=2.38, P<0.001) donors were more likely not to be available compared to Caucasian donors. Female donors were also more likely not to be available (OR=1.32, P<0.001): primarily due to pregnancy. Older donors were less likely to be available in univariate analysis, but this association was not significant after controlling for other factors. Blood donors and those recruited within the past five years had lower rates of attrition. Accumulation of additional attrition-associated characteristics for a given donor was associated with progressively greater odds of attrition (OR 1.99, 2.52, 3.4 and 5.53, respectively, for 1, 2, 3 and 4 risk factors, P<0.001). Donor registries must develop evidence-driven strategies to recruit and retain the most reliable donors.