In a study recently published in TRANSFUSION, researchers from the Canadian Blood Services reported results from routine and quality control screening for bacterial contamination of platelet units over six years. Both buffy coat platelet concentrates (n=601,988) and apheresis platelet concentrates (n=186,737) were collected and screened by culturing samples aerobically at least 24 hours after collection. One percent of outdated units (8535 buffy coat and 8498 apheresis platelet concentrates) were also cultured both aerobically and anaerobically. Based on routine screening, approximately 1 in 10,000 buffy coat and apheresis platelet concentrates were contaminated. However, quality control cultures and the rate of septic transfusion reactions affirm approximately 1 per 1000 contaminated platelet concentrates were missed with an approximate rate of 1:100,000 transfusion reactions and 1:500,000 fatal reactions. In addition, 100% of Gram-negative bacteria were identified, but 90% of Gram-positive bacteria were missed in routine cultures and were responsible for all reported transfusion reactions during the study period. To improve platelet transfusion safety, early screening should be used in conjunction with later testing or an approved pathogen-reduction system, as recently recommended by the U.S. Food and Drug Administration.
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Platelet transfusion safety can also be improved by delaying platelet sampling during early screening with an automated culture system. This strategy has been adopted by the National Health Service Blood and Transplant (UK) and Héma-Québec (Canada).