Improved yield of minimal proportional sample volume platelet bacterial culture

Reports of septic transfusion reactions (STRs) after transfusion of culture-negative platelets (PLTs) justify more effective prevention strategies. Pathogen reduction technologies or performance of additional point-of-issue testing are proposed strategies to enhance safety through Day 5 of storage.

Trima leukoreduced apheresis PLTs (APs) were collected during two study periods (45 and 31 months) using standard procedures, with target settings adjusted during the second period to maintain split rate after increased culture volume. Primary testing for bacterial contamination was performed using BacT/ALERT 3D with sampling from the mother bag 24 to 36 hours after collection. Two culture approaches were compared: in Period A, an 8-mL sample in one aerobic culture bottle (CB), and in Period B a minimal proportional sample volume (PSV) of at least 3.8% of mother bag volume into one to three aerobic CBs (7-10 mL per bottle).

In Periods A and B, 188,389 and 159,098 AP collections were tested, respectively. The true-positive (TP) rate in Period A was 0.90 per 10,000 collections and in Period B was 1.83 per 10,000 (p < 0.05). In Period B, 12 of 29 (41%) TP results had discrepant CB results (DCBRs; at least one of multiple bottles without growth). The false-positive rate in Period B, 15.05 per 10,000 collections, was significantly higher than that of Period A, 3.66 per 10,000. One contaminated collection resulting in STR(s) was reported in each study period. Implementation of PSV was operationally successful and did not impact the AP split rate.

Proportional sample volume improved the sensitivity of primary testing and identified collections that could have escaped detection had only a single bottle with 8- to 10-mL volume been used. PSV may represent another approach to enhanced PLT safety for 5-day storage without a requirement for secondary testing.