Residual Component Culture: Application of Standardized Transfusion Reaction Culture Criteria to Reduce Culture Rates

Abstract

Abstract Blood products are often cultured as part of a transfusion reaction (TRXN) workup in order to “not miss” a septic TRXN. These cultures are vulnerable to secondary contamination and are often challenging to interpret due to the lack of a corresponding patient blood culture. Although bacterial contamination of blood products remains a leading cause of transfusion related fatalities, the actual prevalence of primary contamination of blood components is quite low, leading to a low positive predictive value (PPV) for component culture. Given recently mandated mitigation strategies to reduce bacterial contamination of platelets, the PPV of component culture is likely to further decline, making appropriate selection criteria for culture even more critical to conserve laboratory resources and maximize clinical utility. At our institution the decision to culture is at the discretion of the pathology resident and/or transfusion medicine physician. We sought to review our current culture rates and determine if applying standardized indications for component culture could reduce culture rates without impacting diagnostic utility. Clinical symptoms and vital signs were reviewed for the 24-hour period after the reaction for all TRXNs reported from July 2021 to June 2022. Of the 105 reactions reported during the study timeframe, 39 (37%) were cultured, with one positive culture involving a platelet unit. This was deemed a true septic reaction given concordant cultures in the patient. Modified forms of the AABB and BEST culture criteria were then applied to the reported reactions. Modifications were made to provide specific definitions for tachycardia (heart rate > 100bpm and at least 15% increase) and hypotension (SBP < 80mmhg and at least a 30mmHg decrease). Application of the AABB criteria reduces the number of cultures to 22 (21% of reactions) whereas the BEST criteria increases the number of cultures to 51 (49% of reactions). Both criteria captured the true positive septic reaction. Neither criteria were completely concordant with our current practice. Of the 39 reactions selected for culture by our institution, 26 (67%) did not meet AABB criteria and 11 (28%) did not met BEST criteria; 9 and 22 different reactions would have been cultured based on AABB and BEST criteria respectively. Although we are not able to confirm if culturing of the discrepant units would have yielded additional positive cultures, retrospective chart review did not reveal any additional cases of clinically significant sepsis. The modified AABB criteria decreased the culture rate by 56% while still capturing the true positive septic TRXN suggesting that it would be the best option to reduce the cost/burden of culturing products without reducing diagnostic accuracy. Both published criteria do not take into consideration duration of symptoms and clinical interventions, thus clinical judgement remains critical to the decision to culture.