NaviDx Consulting, Mount Prospect, Illinois, USA.
Department of Pathology, Michigan Medicine, Ann Arbor, Michigan, USA.
J Clin Microbiol. 2022 Jan 19;60(1):e0167521. doi: 10.1128/JCM.01675-21. Epub 2021 Oct 20.
Quality control (QC) rules (Westgard rules) are applied to viral load testing to identify runs that should be reviewed or repeated, but this requires balancing the patient safety benefits of error detection with the cost and inefficiency of false rejection. In this study, we identified the total allowable errors (TEa) from the literature and utilized a commercially available software program (Unity Real Time; Bio-Rad Laboratories) to manage QC data, assess assay performance, and provide QC decision support for both FDA-approved/cleared (Abbott cytomegalovirus [CMV] and HIV viral load) as well as laboratory-developed (Epstein-Barr virus [EBV] viral load) assays. Unity Real Time was used to calculate means, standard deviations (SDs), and coefficient of variation (CV; in percent) of negative, low-positive, and high-positive control data from 73 to 83 days of testing. Sigma values were calculated to measure the test performance relative to a TEa of 0.5 log. The sigma value of 5.06 for EBV predicts ∼230 erroneous results per million individual patient tests (0.02% frequency), whereas sigma values of >6 for CMV (11.32) and HIV (7.66) indicate <4 erroneous results per million individual patient tests. The Unity Real Time QC Design module utilized these sigma values to recommend QC rules and provided objective evidence for loosening the laboratory's existing QC rules for run acceptability, potentially reducing false rejection rates by 10-fold for the assay with the most variation (EBV viral load). This study provides a framework for laboratories, with Unity Real Time as a tool, to evaluate assay performance relative to clinical decision points and establish optimal rules for routine monitoring of molecular viral load assay performance.
质量控制 (QC) 规则（Westgard 规则）应用于病毒载量检测，以识别需要审核或重复的检测批次，但这需要平衡错误检测的患者安全收益与假拒结果的成本和效率。在本研究中，我们从文献中确定了总允许误差（TEa），并利用商业上可用的软件程序（Unity Real Time；Bio-Rad Laboratories）管理 QC 数据、评估检测性能，并为经 FDA 批准/认证的（Abbott 巨细胞病毒 [CMV] 和 HIV 病毒载量）和实验室开发的（EBV 病毒载量）检测提供 QC 决策支持。Unity Real Time 用于计算从 73 天到 83 天检测的阴性、低阳性和高阳性对照数据的平均值、标准差 (SD) 和变异系数 (CV；以百分比表示)。Sigma 值用于衡量相对于 0.5 log TEA 的测试性能。EBV 的 sigma 值为 5.06，预测每百万个体患者检测有 ∼230 个错误结果（频率为 0.02%），而 CMV（11.32）和 HIV（7.66）的 sigma 值>6 表示每百万个体患者检测<4 个错误结果。Unity Real Time QC 设计模块利用这些 sigma 值推荐 QC 规则，并为放宽实验室现有的检测批次可接受性 QC 规则提供客观证据，对于变异最大的检测（EBV 病毒载量），可能将假拒率降低 10 倍。本研究为实验室提供了一个框架，以 Unity Real Time 为工具，评估相对于临床决策点的检测性能，并为常规监测分子病毒载量检测性能建立最佳规则。
