Malan Annette K, Martins Thomas B, Hill Harry R, Litwin Christine M
Associated Regional and University Pathologists Institute for Clinical and Experimental Pathology, Salt Lake City, Utah 84108, USA.
J Clin Microbiol. 2004 Feb;42(2):727-33. doi: 10.1128/JCM.42.2.727-733.2004.
West Nile virus was introduced into the United States in 1999 and in only four seasons has become endemic east of the Rocky Mountains. Recently, immunoglobulin M (IgM)-capture enzyme immunoassays for the detection of West Nile virus-specific IgM and indirect IgG enzyme immunoassays for the detection of IgG antibodies against West Nile virus were made available from Focus Technologies and PANBIO, Inc. We evaluated these commercial IgG and IgM test systems and determined agreement, sensitivity, and specificity for the assays, compared to immunofluorescence assay and the Centers for Disease Control and Prevention's IgM-capture enzyme-linked immunosorbent assay (ELISA). Initially, the Focus and PANBIO IgM enzyme immunoassays had at least 95% agreement, sensitivity, and specificity, and, based on the 95% confidence intervals, both IgM-capture assays performed similarly. The IgG assays also performed well, although the Focus IgG assay demonstrated greater specificity (98.8%) and the PANBIO IgG assay demonstrated greater sensitivity (99.3%). However, for 400 samples consecutively submitted for West Nile virus antibody testing during 2 days of the 2003 West Nile virus season, agreement, clinical sensitivity, and clinical specificity were 93.1, 98.0, and 92.4%, respectively, for the PANBIO IgM assay and were 97.4, 100.0, and 97.1%, respectively, for the Focus IgM assay. The specificities observed in this second evaluation equates to an overall false-positivity rate of 6.3% in the PANBIO West Nile virus IgM-capture ELISA versus 2.5% with the Focus West Nile virus IgM-capture ELISA. This experience demonstrates the importance of continuously evaluating the performance of an assay in order to detect any changes in assay performance as the test population evolves.
西尼罗河病毒于1999年传入美国，仅在四个季节内就在落基山脉以东地区成为地方性流行病。最近，Focus Technologies公司和PANBIO公司推出了用于检测西尼罗河病毒特异性IgM的免疫球蛋白M（IgM）捕获酶免疫测定法以及用于检测抗西尼罗河病毒IgG抗体的间接IgG酶免疫测定法。我们评估了这些商业化的IgG和IgM检测系统，并确定了这些测定法与免疫荧光测定法以及疾病控制与预防中心的IgM捕获酶联免疫吸附测定法（ELISA）相比的一致性、敏感性和特异性。最初，Focus和PANBIO的IgM酶免疫测定法的一致性、敏感性和特异性至少为95%，并且基于95%置信区间，两种IgM捕获测定法的表现相似。IgG测定法也表现良好，尽管Focus IgG测定法显示出更高的特异性（98.8%），而PANBIO IgG测定法显示出更高的敏感性（99.3%）。然而，在2003年西尼罗河病毒流行季的两天内连续提交进行西尼罗河病毒抗体检测的400份样本中，PANBIO IgM测定法的一致性、临床敏感性和临床特异性分别为93.1%、98.0%和92.4%，Focus IgM测定法分别为97.4%、100.0%和97.1%。在第二次评估中观察到的特异性相当于PANBIO西尼罗河病毒IgM捕获ELISA的总体假阳性率为6.3%，而Focus西尼罗河病毒IgM捕获ELISA为2.5%。这一经验表明，随着检测人群的变化，持续评估测定法的性能以检测测定法性能的任何变化非常重要。
