PathLinks Pathology Department, Scunthorpe General Hospital, Cliff Gardens, Scunthorpe, North Lincolnshire DN15 7BH, UK.
Ann Clin Biochem. 2010 Mar;47(Pt 2):165-7. doi: 10.1258/acb.2009.009151. Epub 2010 Feb 11.
It is vital that laboratories participate in External Quality Assurance (EQA) programmes, but results from such schemes do not necessarily help ensure assays are 'in control'. We describe a series of experiments undertaken to explore apparent poor performance in an occult blood EQA scheme that manifested as a series of false-negatives. As a consequence of our laboratory misclassifying some EQA samples, we decided to design a simple sensitivity study that would reaffirm confidence in our testing procedures.
In order to verify analyst reliability and analytical sensitivity, a series of 10 faecal samples were supplemented with increasing amounts of whole blood (0-1.0 mg/Hb/g faeces) and these were then tested independently by four different operatives. EQA samples which our laboratory misclassified were shared with and tested by a second laboratory and results compared.
The results demonstrated consistency in interpretation among the four 'testers' and also suggested that the sensitivity of the method is 0.7 rather than 0.6 mg/Hb/g faeces as claimed by the manufacturer. The second laboratory obtained identical results as our laboratory for the EQA samples which our laboratory had misclassified.
Occult blood EQA scheme results might not give a true reflection of a laboratory's ability to provide reliable results. We would encourage any laboratory observing relative poor performance to undertake local sensitivity studies and repeat testing of EQA samples if in any doubt.
实验室参与外部质量保证（EQA）计划至关重要，但此类计划的结果并不一定能确保检测“处于控制之中”。我们描述了一系列实验，旨在探索在一项潜血 EQA 计划中表现为一系列假阴性的明显性能不佳的情况。由于我们实验室错误地分类了一些 EQA 样本，因此决定设计一项简单的敏感性研究，以重新确认我们的测试程序的信心。
为了验证分析师的可靠性和分析灵敏度，我们用越来越多的全血（0-1.0mg/Hb/g 粪便）补充了一系列 10 份粪便样本，然后由四位不同的操作人员独立测试。我们实验室错误分类的 EQA 样本与第二家实验室共享并进行了测试，并对结果进行了比较。
结果表明四位“测试员”的解释具有一致性，并且还表明该方法的灵敏度为 0.7 而不是制造商声称的 0.6mg/Hb/g 粪便。第二家实验室对我们实验室错误分类的 EQA 样本获得了与我们实验室相同的结果。
潜血 EQA 计划的结果可能无法真实反映实验室提供可靠结果的能力。我们鼓励任何观察到相对较差性能的实验室，如果有任何疑问，进行本地敏感性研究并重复测试 EQA 样本。
