Baruch Joaquin, Suanes Alejandra, Piaggio Jose M, Gil Andres D
Departamento de Bioestadística, Facultad de Veterinaria, Universidad de la Republica, Montevideo, Uruguay.
Center for Outcomes Research and Epidemiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS, United States.
Front Vet Sci. 2020 Apr 15;7:178. doi: 10.3389/fvets.2020.00178. eCollection 2020.
Bovine brucellosis has been under eradication in Uruguay since 1998. The eradication program includes, among other interventions, individual sera sampling of beef animals at slaughter, and annual serum testing of all dairy cows-accounting for two million samples annually. At a herd prevalence of 0.8%, a pooled-sera sample approach could reduce the economic burden of the surveillance system by reducing the testing and operational costs. Our objective was to evaluate the analytic sensitivity of an indirect ELISA test for in serum pools. Sixty-two positive bovine sera samples (based upon rose bengal and fluorescent polarization assay) were used as the positive control samples. Rose bengal-negative sera from negative farms were used to dilute the positive samples to the desired concentrations. Positive samples were diluted by using 1 ml of positive sera and 1 ml of negative sera (1/2 dilution) up to 1/1,024. Data were analyzed using generalized linear mixed models with a binary outcome (positive or negative), dilution number as a fixed effect, and a random effect for sample ID. Analytic sensitivity was 99.0% [95% confidence interval (CI): 96.3-99.7], 98.3% (95% CI: 93.1-99.6), 97.3% (95% CI: 87.4-99.4) for dilutions 1/2, 1/4, and 1/8, respectively. The analytical sensitivity, however, decreased when diluted to greater proportions. Given the current herd prevalence in Uruguay, it seems plausible that the use of a pooled sample approach could be adopted by policymakers to reduce the cost of the surveillance program and increase the number of samples being tested.
自1998年以来，乌拉圭一直在开展牛布鲁氏菌病根除工作。根除计划包括多项干预措施，其中有在肉牛屠宰时对个体进行血清采样，以及对所有奶牛进行年度血清检测——每年检测样本达两百万份。在畜群患病率为0.8%的情况下，采用混合血清样本方法可以通过降低检测和运营成本来减轻监测系统的经济负担。我们的目标是评估间接ELISA检测血清池的分析灵敏度。62份经虎红平板凝集试验和荧光偏振试验检测为阳性的牛血清样本用作阳性对照样本。来自阴性农场的虎红平板凝集试验阴性血清用于将阳性样本稀释至所需浓度。阳性样本通过将1毫升阳性血清和1毫升阴性血清混合（1/2稀释）进行稀释，直至1/1024。数据采用广义线性混合模型进行分析，以二元结果（阳性或阴性）、稀释倍数作为固定效应，并以样本ID作为随机效应。对于1/2、1/4和1/8的稀释度，分析灵敏度分别为99.0%[95%置信区间（CI）：96.3 - 99.7]、98.3%（95%CI：93.1 - 99.6）、97.3%（95%CI：87.4 - 99.4）。然而，当稀释比例更高时，分析灵敏度会降低。鉴于乌拉圭目前的畜群患病率，政策制定者采用混合样本方法以降低监测计划成本并增加检测样本数量似乎是可行的。
