A meta-analysis of five published case-control studies that examined the association between previous blood transfusions and Creutzfeld-Jakob disease was performed. The results demonstrated that controls were more likely (p < 0.001, odds ratio = 1.56, 95% confidence interval, 1.22-1.98) to have received previous blood transfusions (18.7%) than Creutzfeld-Jakob disease patients (12.9%), suggesting that selection bias of the control populations had occurred.