Quality control perspectives: Weak signal detection to prevent clinical sensitivity failures in donor screening

Ensuring the accuracy of donor screening examinations is critical to minimizing the risk of transfusion-transmissible infections. Weak signals, which refer to low-intensity examination responses near the detection threshold, pose a challenge in distinguishing true positive results from background noise, which leads to the increasing likelihood of misclassification. Screening immunoassays are more susceptible to weak signal issues than nucleic acid tests (NAT) due to the inherent amplification step in NAT, which enhances sensitivity. This article explores the risks associated with weak signal detection failures, the necessity of cutoff protection, and the role of verification and validation targeted samples. Additionally, it discusses the importance of internal quality control and external quality assessment strategies to mitigate the limitations of using high-signal samples in donor screening.