Screening of single-donor apheresis platelets for bacterial contamination: the PASSPORT study results

The PASSPORT study was an FDA-mandated surveillance of outdated 7-day apheresis platelets (APs) to assess the bacterial culture release test (RT) performance and the chance of transfusing APs containing viable bacteria compared to untested 5-day APs.

Aerobic and anaerobic culture bottles were inoculated with 4 to 5 mL from APs 24 to 36 hours postcollection. APs were released after 24 hours if no growth was observed. Released APs were recalled for RT positives, and clinical services were notified. Day 8 APs were recultured (surveillance test [ST]). Initially positive RTs and STs were confirmed by AP reculture.

A total of 388,903 RTs were accrued September 2005 through January 2008 from 52 regional blood centers: RT-positive APs interdicted before transfusion, 76 true positive (TP; 195/million; 95% confidence interval [CI], 154-244/million) and 57 indeterminate (IN); and RT-positive APs transfused, 14 TP and 242 IN. There were 14 reported septic transfusion reactions (STRs) from 13 AP collections (23 units) transfused on Days 3 through 7; three STRs were from Day 6 or 7 APs. There were two false-negative RTs causing STRs in three patients. No deaths were reported. STs had four TPs of 6039 tested (662/million; 95% CI, 180-1695/million).

RT culturing prevents issuance of some bacterially contaminated APs. ST culture data and clinical reports suggest that this screening fails to detect all contaminated units. No fatalities were reported related to AP transfusion. Additional actions or testing may be required to further reduce the residual STR risk of RT APs, even with a 5-day storage limitation.