Jenny R W, Jackson-Tarentino K Y
Laboratory for Molecular Diagnostics, Division of Molecular Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA.
Clin Chem. 2000 Jan;46(1):89-99.
Proficiency testing (PT) provides a measure of the effectiveness of laboratory quality assurance programs. Test reports are released from processes that the laboratory judges to be in conformance with quality specifications; an evaluation of unsatisfactory performance (UNSAT) by a PT provider is an unexpected outcome for the laboratory. An understanding of the root cause(s) of testing errors provides an opportunity for the continuous improvement of laboratory services.
We used participant data from the New York State Department of Health PT program to characterize the quality of testing in the toxicology specialty. Outcomes from laboratory investigations into causes of UNSAT and information on quality control practices collected from all program participants were used to identify the root causes of error.
Two classes of error were encountered: spurious test results caused by lapses in standard operating procedures and instrument malfunctions (300 per million assays) and common-cause analytic error (7000 per million assays or 0.7% rate of UNSAT). Causes of spurious results included inaccurate mathematical correction for specimen dilution, misinterpretation of instrument codes, and instrument sampling errors. Calibration drift was most frequently cited as the common-cause analytic error. Approximately one-half of the laboratories used an allowable error for the quality control of analytical systems that exceeded the threshold error specified by manufacturers for stable instrument performance.
The causes of spurious results suggest the need for ongoing competency testing of analysts where analyst intervention is required in an otherwise automated process, and for continued diligence in mistake-proofing instrument design. The intrinsic quality of laboratory testing is unlikely to improve until the allowable error in quality control is consistent with manufacturer specifications for stable system performance.
能力验证（PT）可衡量实验室质量保证计划的有效性。测试报告由实验室判定符合质量规范的流程发布；PT提供者对不满意表现（UNSAT）的评估对实验室来说是意外结果。了解测试错误的根本原因可为实验室服务的持续改进提供契机。
我们使用了纽约州卫生部PT计划的参与者数据来描述毒理学专业的测试质量。实验室对UNSAT原因的调查结果以及从所有计划参与者收集的质量控制实践信息用于确定错误的根本原因。
遇到了两类错误：由标准操作程序失误和仪器故障导致的虚假测试结果（每百万次分析300次）以及常见原因分析错误（每百万次分析7000次或UNSAT率为0.7%）。虚假结果的原因包括标本稀释的数学校正不准确、仪器代码解读错误以及仪器采样错误。校准漂移最常被列为常见原因分析错误。约一半的实验室在分析系统质量控制中使用的允许误差超过了制造商规定的仪器稳定性能阈值误差。
虚假结果的原因表明，在需要分析人员干预的自动化流程中，需要持续对分析人员进行能力测试，并且在仪器设计防错方面要持续保持严谨。在质量控制中的允许误差与制造商规定的系统稳定性能规范一致之前，实验室测试的内在质量不太可能提高。
