Wood Caitlin, Muleme Michael, Tan Tabita, Bosward Katrina, Gibson Justine, Alawneh John, McGowan Michael, Barnes Tamsin S, Stenos John, Perkins Nigel, Firestone Simon M, Tozer Sarah
The University of Queensland, School of Veterinary Science, Gatton, Queensland, 4343, Australia; Centre for Children's Health Research, Queensland Paediatric Infectious Disease Laboratory, Lady Cilento Research Precinct, South Brisbane, Queensland, 4101, Australia.
The University of Melbourne, Asia-Pacific Centre for Animal Health, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, Parkville Victoria, 3010, Australia.
Prev Vet Med. 2019 Aug 1;169:104698. doi: 10.1016/j.prevetmed.2019.104698. Epub 2019 May 23.
There is limited knowledge of the true prevalence and distribution of coxiellosis in dairy and beef cattle populations in Australia. For this to occur, apparent prevalence estimates need to be reliably adjusted, accounting for diagnostic sensitivity (DSe) and diagnostic specificity (DSp) of the test used. However, there are few tests available with known diagnostic specifications suitable to inform screening and surveillance activities in the Australian context. We initially modified and optimised a human indirect immunofluorescence assay (IFA) test for the detection of IgG antibodies against phase I and/or phase II Coxiella burnetii in bovine sera and determined an optimal screening dilution cut-off to be 1:160. Direct comparison of the modified IFA with the commercial IDEXX enzyme-linked immunosorbent assay (ELISA) kit (Q Fever Ab Test IDEXX Laboratories, United States of America) was performed by testing 458 serum samples from four distinct cattle populations across the east coast of Australia and New Zealand. Cross classified test results were then analysed using Bayesian latent class modelling, to validate the tests in the absence of a gold standard reference test. Results from this analysis indicate that the IFA, at a 1:160 serum dilution, has an estimated DSe of 73.6% (95% Credible Interval (CrI) 61.1, 85.9) and DSp of 98.2% (95% CrI 95.1, 99.7). The commercial IDEXX ELISA kit was found to have a higher DSe of 87.9% (95% CrI 73.9, 96.4) and similar DSp of 97.7% (95% CrI 93.2, 99.7). Evaluation of the diagnostic performance of the IFA and ELISA methods, specifically for use in cattle will enable more accurate interpretation of prevalence estimates of C. burnetii exposure to be reported for cattle in Australia and other countries.
关于澳大利亚奶牛和肉牛群体中柯克斯体病的真实流行率和分布情况，人们了解有限。要做到这一点，需要根据所用检测方法的诊断敏感性（DSe）和诊断特异性（DSp），对表观流行率估计值进行可靠调整。然而，在澳大利亚的情况下，适合用于筛查和监测活动且具有已知诊断规格的检测方法很少。我们最初对一种人类间接免疫荧光测定法（IFA）进行了修改和优化，用于检测牛血清中针对Ⅰ期和/或Ⅱ期伯氏考克斯体的IgG抗体，并确定最佳筛查稀释临界值为1:160。通过检测来自澳大利亚东海岸和新西兰四个不同牛群的458份血清样本，将改良后的IFA与商业IDEXX酶联免疫吸附测定试剂盒（Q热抗体检测试剂盒，IDEXX实验室，美国）进行了直接比较。然后使用贝叶斯潜在类别模型分析交叉分类的检测结果，以在没有金标准参考检测的情况下验证这些检测方法。该分析结果表明，在血清稀释度为1:160时，IFA的估计DSe为73.6%（95%可信区间（CrI）61.1，85.9），DSp为98.2%（95%CrI 95.1，99.7）。发现商业IDEXX ELISA试剂盒具有更高的DSe，为87.9%（95%CrI 73.9，96.4），DSp相似，为97.7%（95%CrI 93.2，99.7）。对IFA和ELISA方法的诊断性能进行评估，特别是用于牛的情况，将有助于更准确地解释澳大利亚和其他国家报告的牛感染伯氏考克斯体的流行率估计值。
