Department of Mathematics, University of Utah, Salt Lake City, Utah, USA.
ARUP Laboratories, Salt Lake City, Utah, USA.
Transfusion. 2021 Mar;61(3):873-882. doi: 10.1111/trf.16258. Epub 2021 Jan 11.
The US Food and Drug Administration (FDA) issued a guidance for bacterial risk control strategies for platelet components in September 2019 that includes strategies using secondary bacterial culture (SBC). While an SBC likely increases safety, the optimal timing of the SBC is unknown. Our aim was to develop a model to provide insight into the best time for SBC sampling.
We developed a mathematical model based on the conditional probability of a bacterial contamination event. The model evaluates the impact of secondary culture sampling time over a range of bacterial contamination scenarios (lag and doubling times), with the primary outcome being the optimal secondary sampling time and the associated risk.
Residual risk of exposure decreased with increasing inoculum size, later sampling times for primary culture, and using higher thresholds of exposure (in colony-forming units per milliliter). Given a level of exposure, the optimal sampling time for secondary culture depended on the timing of primary culture and on the expiration time. In general, the optimal sampling time for secondary culture was approximately halfway between the time of primary culture and the expiration time.
Our model supports that the FDA guidance is quite reasonable and that sampling earlier in the specified secondary culture windows may be most optimal for safety.
美国食品和药物管理局（FDA）于 2019 年 9 月发布了血小板成分细菌风险控制策略指南，其中包括使用二级细菌培养（SBC）的策略。虽然 SBC 可能会提高安全性，但 SBC 的最佳时间尚不清楚。我们的目的是开发一种模型，以深入了解 SBC 采样的最佳时间。
我们基于细菌污染事件的条件概率开发了一个数学模型。该模型评估了在一系列细菌污染情况下（滞后和倍增时间）二级培养采样时间的影响，主要结果是最佳二级采样时间和相关风险。
随着接种物数量的增加、初级培养时的采样时间延迟以及使用更高的暴露阈值（每毫升形成菌落的单位数），暴露的残余风险降低。给定暴露水平，二级培养的最佳采样时间取决于初级培养的时间和到期时间。一般来说，二级培养的最佳采样时间大约是初级培养和到期时间之间的中点。
我们的模型支持 FDA 指南相当合理，并且在指定的二级培养窗口中更早采样可能对安全性最为优化。
