Evaluation of blood lead proficiency testing: comparison of open and blind paradigms.

BACKGROUND Most proficiency testing (PT) programs operate with an open design in which clearly identified performance samples are distributed directly to participating laboratories on a shipping schedule announced in advance. In this study, we examine the effectiveness of assessing clinical laboratory performance for blood lead with an open PT by comparing its results with a double-blinded testing protocol. METHODS Aliquots from up to 72 blood lead performance pools from the New York State Department of Health and the Wisconsin State Laboratory of Hygiene were disguised as routine patient specimens and submitted in two phases to up to 42 certified clinical laboratories for blood lead analysis. These 42 laboratories also received aliquots of the same performance samples for blood lead analysis directly from the "open" PT program provider. RESULTS Data reported under blind and open strategies were scored against acceptable target ranges using the Clinical Laboratory Improvement Amendments of 1988 (CLIA '88) criteria established for blood lead, i.e., +/- 0.19 micromol/L (+/- 4 microg/dL) or +/- 10%, whichever is greater. Performance differences between the strategies were also assessed. We found that 17.7% of all blind PT results were classified as unacceptable compared with only 4.5% of open PT results (P <0.001). In phase 1, 13 of 22 laboratories (60%) exhibited a statistically significant difference (P <0.05) between their blind and open PT performances, although for 6 laboratories the poorer blind performance may not necessarily have led to unsuccessful PT participation under CLIA '88 criteria. Seven (32%) laboratories had unsuccessful aggregate performance (<80%) under blind testing while maintaining successful performance in open testing. Of these seven, two had gross discrepancies motivating further investigation. CONCLUSIONS The data suggest that although approximately 60% of clinical laboratories make special efforts to improve analytical performance on open PT samples relative to performance achieved for routine patient specimens, in most cases the differences are clinically insignificant and would not likely affect cumulative PT performance. Occasional use of blind PT may deter the inclination to treat performance samples more carefully.

背景 大多数能力验证（PT）项目采用开放式设计，即按照预先公布的发货时间表，将明确标识的能力验证样本直接分发给参与实验室。在本研究中，我们通过将开放式能力验证结果与双盲测试方案的结果进行比较，来检验其评估血铅临床实验室能力的有效性。 方法 来自纽约州卫生部和威斯康星州卫生实验室的多达72个血铅能力验证样本被伪装成常规患者标本，并分两个阶段提交给多达42个经认证的临床实验室进行血铅分析。这42个实验室也直接从“开放式”能力验证项目提供者那里收到了相同能力验证样本的等分试样用于血铅分析。 结果 根据1988年临床实验室改进修正案（CLIA '88）为血铅制定的标准，即±0.19 μmol/L（±4 μg/dL）或±10%（以较大者为准），对盲法和开放法策略下报告的数据针对可接受的目标范围进行评分。还评估了两种策略之间的性能差异。我们发现，所有盲法能力验证结果中有17.7%被归类为不可接受，而开放法能力验证结果中只有4.5%（P <0.001）。在第一阶段，22个实验室中有13个（60%）在其盲法和开放法能力验证表现之间存在统计学上的显著差异（P <0.05），尽管对于6个实验室来说，较差的盲法表现不一定会导致在CLIA '88标准下能力验证参与不成功。7个（32%）实验室在盲法测试下总体表现不成功（<80%），但在开放法测试中保持成功表现。在这7个实验室中，有2个存在严重差异，值得进一步调查。 结论 数据表明，尽管大约60%的临床实验室相对于常规患者标本的检测表现，会特别努力提高对开放式能力验证样本的分析性能，但在大多数情况下，这些差异在临床上并不显著，不太可能影响累计的能力验证表现。偶尔使用盲法能力验证可能会抑制对能力验证样本更谨慎对待的倾向。