['Acute intravascular hemolysis after exchange transfusion with glucose 6-phosphate dehydrogenase-deficient blood has been reported; however, it is not routine to screen donor blood for glucose 6-phosphate dehydrogenase deficiency while performing exchange transfusion. We hypothesized that exchange transfusion with glucose 6-phosphate dehydrogenase-deficient blood would lead to a less-than-expected decrease in total serum bilirubin. The objective of this study was to evaluate the effect of exchange transfusion with glucose 6-phosphate dehydrogenase-deficient blood in neonates with idiopathic hyperbilirubinemia on postexchange total serum bilirubin levels, duration of phototherapy, and need for repeat exchange transfusions.', 'All neonates who were undergoing exchange transfusion for idiopathic hyperbilirubinemia were enrolled. A sample of donor blood was collected at the time of exchange transfusion for a glucose 6-phosphate dehydrogenase assay. The standard criteria for starting and stopping phototherapy and exchange transfusion were applied.', 'During the 1-year study period, 21 infants underwent exchange with glucose 6-phosphate dehydrogenase-deficient blood, and 114 neonates with similar baseline characteristics underwent exchange transfusion with glucose 6-phosphate dehydrogenase-normal blood. From 6 to 60 hours after exchange transfusion, there was a significantly lesser drop in total serum bilirubin in the recipients of glucose 6-phosphate dehydrogenase-deficient donor blood compared with recipients of glucose 6-phosphate dehydrogenase-normal blood. The mean duration of phototherapy in the postexchange period and number of infants who underwent repeat exchange transfusions were significantly higher in recipients of glucose 6-phosphate dehydrogenase-deficient donor blood in comparison with control subjects. Concurrently, there was a significantly higher drop in hematocrit and rise in plasma hemoglobin in the glucose 6-phosphate dehydrogenase-deficient donor group.'] Does donor blood glucose 6-phosphate dehydrogenase deficiency reduce the efficacy of exchange transfusion in neonatal hyperbilirubinemia?