Norwegian Porphyria Centre (NAPOS), Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway.
Clin Chem. 2011 Nov;57(11):1514-23. doi: 10.1373/clinchem.2011.170357. Epub 2011 Sep 21.
The porphyrias are a group of rare metabolic disorders whose diagnosis depends on identification of specific patterns of porphyrin precursor and porphyrin accumulation in urine, blood, and feces. Diagnostic tests for porphyria are performed by specialized laboratories in many countries. Data regarding the analytical and diagnostic performance of these laboratories are scarce.
We distributed 5 sets of multispecimen samples from different porphyria patients accompanied by clinical case histories to 18-21 European specialist porphyria laboratories/centers as part of a European Porphyria Network organized external analytical and postanalytical quality assessment (EQA) program. The laboratories stated which analyses they would normally have performed given the case histories and reported results of all porphyria-related analyses available, interpretative comments, and diagnoses.
Reported diagnostic strategies initially showed considerable diversity, but the number of laboratories applying adequate diagnostic strategies increased during the study period. We found an average interlaboratory CV of 50% (range 12%-152%) for analytes in absolute concentrations. Result normalization by forming ratios to the upper reference limits did not reduce this variation. Sixty-five percent of reported results were within biological variation-based analytical quality specifications. Clinical interpretation of the obtained analytical results was accurate, and most laboratories established the correct diagnosis in all distributions.
Based on a case-based EQA scheme, variations were apparent in analytical and diagnostic performance between European specialist porphyria laboratories. Our findings reinforce the use of EQA schemes as an essential tool to assess both analytical and diagnostic processes and thereby to improve patient care in rare diseases.
卟啉症是一组罕见的代谢紊乱疾病，其诊断依赖于尿液、血液和粪便中特定类型的卟啉前体和卟啉积累的识别。卟啉症的诊断测试由许多国家的专业实验室进行。关于这些实验室的分析和诊断性能的数据很少。
我们将 5 套来自不同卟啉症患者的多标本样本与临床病史一起分发给 18-21 个欧洲专业卟啉症实验室/中心，作为欧洲卟啉症网络组织的外部分析和分析后质量评估 (EQA) 计划的一部分。实验室根据病史陈述了他们通常会进行哪些分析，并报告了所有与卟啉症相关的可用分析结果、解释性评论和诊断。
报告的诊断策略最初显示出相当大的多样性，但在研究期间，应用适当诊断策略的实验室数量有所增加。我们发现分析物的平均实验室间变异系数为 50%（范围为 12%-152%）。通过与参考上限形成比值来对结果进行归一化并不能降低这种变异性。65%的报告结果在基于生物学变异的分析质量规范内。获得的分析结果的临床解释是准确的，大多数实验室在所有分配中都建立了正确的诊断。
基于基于病例的 EQA 方案，欧洲专业卟啉症实验室之间的分析和诊断性能存在差异。我们的发现强化了 EQA 方案作为评估分析和诊断过程的重要工具的使用，从而改善了罕见疾病患者的护理。
