Bacterial screening of apheresis platelets and the residual risk of septic transfusion reactions: the American Red Cross experience (2004-2006)

BACKGROUND: The American Red Cross initiated systemwide bacterial testing of all apheresis platelet (PLT) collections in March 2004, yet continues to receive reports of septic reactions after transfusion of screened components. STUDY DESIGN AND METHODS: The rates of confirmed bacterial contamination of apheresis PLT collections detected by prospective quality control (QC) testing, and by surveillance of reported septic reactions to screened-negative apheresis PLTs, were analyzed according to the technology utilized for collection. RESULTS: Between March 1, 2004, and May 31, 2006, bacterial culture testing was performed on 1,004,206 donations; of these, 186 (1:5,399) had confirmed-positive culture results. Transfusion of all but 1 of the associated 293 components was prevented. A significantly higher rate of confirmed-positive bacterial cultures was seen with products collected utilizing two-arm collection procedures compared to one-arm procedures (22.7 vs. 11.9 per 10(5) donations; odds ratio [OR], 1.9; 95% confidence interval [Cl], 1.4-2.7). During this period, 20 septic transfusion reactions were reported, including 3 fatalities (1:498,711 fatalities per distributed component), which implicated screened-negative apheresis PLT products. The frequency of septic reactions was 4.7-fold higher for collections utilizing two-arm procedures (1:41,173; 95% Cl, 1:25,000-1:66,667) compared to collections from one-arm procedures (1:193,305; 95% Cl, 1:52,632-1:500,000; OR, 4.7; 95% Cl, 1.2-18.4); most septic reactions (16 of 20) were due to Staphylococcus spp. and occurred on Day 5 (13 of 20) after collection. CONCLUSION: PLT contamination with bacteria that evade detection by QC culture remains a significant residual transfusion risk, in particular for older PLTs and skin-commensal bacteria in components collected by two-arm apheresis procedures during the study period.