Routine bacterial screening of platelet concentrates by flow cytometry and its impact on product safety and supply

Background and Objectives Bacterial contamination represents the major infectious hazard associated with transfusion of platelet concentrates ( PC s). As bacterial screening of PC s is not mandatory in G ermany, the B acti F low flow cytometry test has been introduced as a rapid detection method to increase product safety. Materials and Methods During a period of 25 months, a total of 34 631 PC s (26 411 pooled and 8220 apheresis‐derived PC s) were tested at the end of day 3 of their shelf life using the B acti F low system. PC s initially reactive in B acti F low testing and expired PC s not reactive in B acti F low on day 3 were also investigated by the B ac T / ALERT system and by microbiological cultivation in order to identify the contaminating bacterial species and to confirm reactive B acti F low results. Results Two hundred and twenty‐eight PC s (0·7%) had an initially reactive result, 24 of them remained reactive in a second test run. Out of these reproducible reactive B acti F low results, 12 could not be verified by parallel B ac T / ALERT culturing, resulting in a confirmed false‐positive rate of 0·03%. The bacterial species were identified as S . aureus , S . epidermidis , S . dysgalactiae ssp. equisimilis and B . cereus . In 10 out of 9017 expired PC s (0·11%), a confirmed‐positive result was obtained in the B ac T / ALERT system which had a negative result in the B acti F low system. Conclusion Testing of PC s by B acti F low was successfully implemented in our blood donation service and proved sufficient as a rapid and reliable screening method. False reactive results are in an acceptable range since the transfusion of 12 bacterially contaminated PC s was prevented.