Niedrig Matthias, Donoso Mantke Oliver, Altmann Doris, Zeller Hervé
Centre for Biological Safety (ZBS-1), Robert Koch-Institut, Nordufer 20, Berlin, Germany.
BMC Infect Dis. 2007 Jul 3;7:72. doi: 10.1186/1471-2334-7-72.
The diagnosis of an acute or convalescent West Nile (WN) virus infection can be confirmed by various serological assays such as enzyme immunoassay (EIA), immunofluorescence assay (IFA), or neutralisation test (NT) which are conducted by a growing number of laboratories. However, as the degree of proficiency may vary between laboratories, quality control measures for laboratory diagnostics are essential.
We have performed an external quality assurance (EQA) programme for the serological detection of WN virus infection to assess the diagnostic quality of laboratories. The participating laboratories received a proficiency panel of 10 coded lyophilised test samples comprising four antisera positive for WN antibodies as positive controls, three antisera positive for antibodies against other heterologous flaviviruses plus one multireactive unspecific serum as specificity controls, and two negative serum samples.
Twenty-seven laboratories from 20 different countries in Europe, the Middle East, the Americas and Africa participated in this EQA programme. Applying the proficiency criteria of this study, only eight laboratories correctly analysed all samples with their respective EIA, IFA or NT methods. Eighteen laboratories correctly identified between 77.8 and 90% of the samples, and one laboratory identified only 70% correctly with a clear need to eliminate cross-reactivity with other antisera, particularly those elicited by yellow fever virus. Differentiation between the results for IgM and IgG was considered separately and revealed that IgM-antibodies were detected less frequently than IgG-antibodies (p < 0.001). However, the assay used was not a significant technical factor influencing laboratory performance.
The EQA programme provides information on the quality of different serological assays used by the participating laboratories and indicates that most need to improve their assays, in particular to avoid cross-reactions with antibodies to heterologous flaviviruses.
急性或恢复期西尼罗河（WN）病毒感染的诊断可通过多种血清学检测方法来确认，如酶免疫测定（EIA）、免疫荧光测定（IFA）或中和试验（NT），越来越多的实验室都在开展这些检测。然而，由于各实验室的熟练程度可能有所不同，实验室诊断的质量控制措施至关重要。
我们开展了一项针对WN病毒感染血清学检测的外部质量保证（EQA）计划，以评估各实验室的诊断质量。参与实验室收到一组包含10个编码冻干检测样本的能力验证样本，其中包括4份WN抗体阳性抗血清作为阳性对照，3份针对其他异源黄病毒抗体阳性的抗血清以及1份多反应性非特异性血清作为特异性对照，还有2份阴性血清样本。
来自欧洲、中东、美洲和非洲20个不同国家的27个实验室参与了该EQA计划。按照本研究的能力验证标准，只有8个实验室使用各自的EIA、IFA或NT方法正确分析了所有样本。18个实验室正确识别了77.8%至90%的样本，1个实验室仅正确识别了70%，明显需要消除与其他抗血清的交叉反应，尤其是由黄热病病毒引发的交叉反应。分别考虑IgM和IgG结果的差异，发现IgM抗体的检测频率低于IgG抗体（p<0.001）。然而，所使用的检测方法并非影响实验室表现的显著技术因素。
该EQA计划提供了关于参与实验室所使用的不同血清学检测质量的信息，并表明大多数实验室需要改进其检测方法，特别是要避免与异源黄病毒抗体发生交叉反应。
