Mercader Sara, Garcia Philip, Bellini William J
Centers For Disease Control and Prevention, Atlanta, Georgia, USA.
Clin Vaccine Immunol. 2012 Nov;19(11):1810-7. doi: 10.1128/CVI.00406-12. Epub 2012 Sep 12.
In regions where endemic measles virus has been eliminated, diagnostic assays are needed to assist in correctly classifying measles cases irrespective of vaccination status. A measles IgG avidity assay was configured using a commercially available measles-specific IgG enzyme immunoassay by modifying the protocol to include three 5-min washes with diethylamine (60 mM; pH 10.25) following serum incubation; serum was serially diluted, and the results were expressed as the end titer avidity index. Receiver operating characteristic analysis was used for evaluation and validation and to establish low (≤30%) and high (≥70%) end titer avidity thresholds. Analysis of 319 serum specimens expected to contain either high- or low-avidity antibodies according to clinical and epidemiological data indicated that the assay is highly accurate, with an area under the curve of 0.998 (95% confidence interval [CI], 0.978 to 1.000), sensitivity of 91.9% (95% CI, 83.2% to 97.0%), and specificity of 98.4% (95% CI, 91.6% to 100%). The assay is rapid (<2 h) and precise (standard deviation [SD], 4% to 7%). In 18 samples from an elimination setting outbreak, the assay identified 2 acute measles cases with low-avidity results; both were IgM-positive samples. Additionally, 11 patients (15 samples) with modified measles who were found to have high-avidity IgG results were classified as secondary vaccine failures; one sample with an intermediate-avidity result was not interpretable. In elimination settings, measles IgG avidity assays can complement existing diagnostic tools in confirming unvaccinated acute cases and, in conjunction with adequate clinical and epidemiologic investigation, aid in the classification of vaccine failure cases.
在已消除地方性麻疹病毒的地区，需要诊断检测方法来协助正确分类麻疹病例，无论其疫苗接种状况如何。通过修改方案，使用市售的麻疹特异性IgG酶免疫测定法构建了麻疹IgG亲和力测定法，即在血清孵育后用二乙胺（60 mM；pH 10.25）进行三次5分钟洗涤；血清进行系列稀释，结果以终点效价亲和力指数表示。采用受试者操作特征分析进行评估和验证，并确定低（≤30%）和高（≥70%）终点效价亲和力阈值。根据临床和流行病学数据对319份预期含有高亲和力或低亲和力抗体的血清标本进行分析，结果表明该检测方法高度准确，曲线下面积为0.998（95%置信区间[CI]，0.978至1.000），灵敏度为91.9%（95%CI，83.2%至97.0%），特异性为98.4%（95%CI，91.6%至100%）。该检测方法快速（<2小时）且精确（标准差[SD]，4%至7%）。在一次消除背景下的疫情中的18份样本中，该检测方法鉴定出2例急性麻疹病例，其亲和力结果较低；这两份样本均为IgM阳性。此外，11例患有变异型麻疹且IgG亲和力结果较高的患者被归类为继发性疫苗失败；1份亲和力结果中等的样本无法解释。在消除背景下，麻疹IgG亲和力检测方法可以补充现有的诊断工具，以确认未接种疫苗的急性病例，并结合充分的临床和流行病学调查，有助于对疫苗失败病例进行分类。
