Background: Bacterial contamination of platelet units poses one of the greatest risks of morbidity and mortality to platelet transfusion recipients. A routine culture of all units (WBC-reduced apheresis platelet units) was instituted on Day 2 over a 2-year period to reduce this risk.
Study design and methods: A sterile connecting device was used to attach a small transfer pack on the morning of Day 2 after collection, and 10 mL of the unit were transferred to the small bag. After disconnection from the unit, about half of this volume was transferred to an aerobic culture bottle of an automated bacterial detection system. Units were maintained in available inventory until and unless a report was received of growth in the sample. When available, the unit or a retained aliquot was recultured if the initial sample was positive. Units were held up to 2 days beyond their 5-day outdate and used for transfusion if no other suitable units were available to meet the clinical need or were evaluated with in vitro testing on Day 8.
Results: Of 2678 units cultured, 16 (0.6%) were positive on initial culture. Thirteen could be recultured, and all of these samples were negative. Shortly after the 2-year period of the study, two units (split from the same collection) were documented as growing coagulase-negative Staphylococci 12 hours after sampling. Units transfused on Day 6 or 7 (n = 40) yielded expected clinical responses, and CCI available on 21 cipients 10 to 60 minutes after transfusion demonstrated acceptable results (mean, 14,400 +/- 8800; median, 12,191; 90% > 7500). More than 96 percent of units tested on Day 8 had pH greater than 6.2 and continued to demonstrate swirling.
Conclusions: Routine culturing of apheresis platelet units is feasible, can be accomplished with a low rate of false positivity, and can detect contaminated units. The cost of such a protocol could be mitigated with extension of the storage period, and clinical experience with units held for 6 or 7 days was satisfactory.