Bacterial testing of platelets – has it prevented transfusion‐transmitted bacterial infections in Australia?

Background and Objectives Australia introduced bacterial contamination screening ( BCS ) for platelet components in April 2008. This study presents analysis performed to assess the efficacy of testing. Materials and Methods Seven‐day aerobic and anaerobic culture is performed using the BacT/ ALERT 3D system. Following an initial machine positive ( IMP ) flag, all associated components are recalled, and/or clinicians treating already transfused patients are notified. IMP s are categorized as ‘machine false positive’, ‘confirmed positive’ or ‘indeterminate’ depending on culture results of initial and repeat samples. Results Between 2010 and 2012, 1·1% of platelet donations tested IMP ; since 2013, this rate has fallen to 0·6% through improved instrument management, reducing false‐positive IMP s but maintaining sensitivity for cultures yielding bacterial growth. On average, 66% of confirmed positive and indeterminate platelet units had been transfused at the time of detection. The majority (95%) of these grew Propionibacterium sp., a slow‐growing organism that rarely causes sepsis in the transfusion setting. The incidence of reported transfuion‐transmitted bacterial infection ( TTBI ) has fallen since the introduction of BCS , with a 4·2‐fold [0·5, 28·2] lower rate from platelets. Conclusion BCS has been successful in detecting platelet units containing pathogenic bacteria. The incidence of TTBI from platelets has fallen since the introduction of BCS , but the risk has not been eliminated due to rare false‐negative results. In the absence of a pathogen inactivation system for red blood cells, BCS provides ‘surrogate’ testing of red blood cells from which platelets have been manufactured.