Goodchild A V, Downs S H, Upton P, Wood J L N, de la Rua-Domenech R
Department of Epidemiological Sciences, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone KT15 3NB, UK.
Data Sciences Group, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone KT15 3NB, UK.
Vet Rec. 2015 Sep 12;177(10):258. doi: 10.1136/vr.102961. Epub 2015 Sep 2.
A novel method for estimating specificity of the Single Intradermal Comparative Cervical Tuberculin (SICCT) test for bovine tuberculosis (bTB) using surveillance tests results is reported. The specificity of the SICCT test at three cut-offs was estimated from the dates, locations and skinfold measurements of all routine tests carried out in Officially TB Free (OTF) cattle herds in Great Britain (GB) between 2002 and 2008, according to their separation (by distance and time) from known infected (OTF-withdrawn) herds. The proportion of animals that tested positive was constant (P>0.20) when the distance between tested herds and nearest infected herd exceeded 8 km. For standard cut-off, calculated specificity was 99.98 per cent (95 per cent confidence interval ±0.004 per cent), equating to one false positive result per 5000 uninfected animals tested. For severe cut-off it was 99.91 per cent (±0.013 per cent) and for ultrasevere cut-off (selecting all reactors and inconclusive reactors) it was 99.87 per cent (±0.017 per cent). The estimated positive predictive value of the test averaged 91 per cent and varied by regional prevalence. This study provides further evidence of the high specificity of the SICCT test under GB conditions, suggests that over 90 per cent of cattle currently culled using this test in GB were infected, and endorses slaughter of at least these cattle for bTB control.
本文报道了一种利用监测测试结果估算单剂量皮内比较颈侧结核菌素试验（SICCT）对牛结核病（bTB）特异性的新方法。根据2002年至2008年期间在英国（GB）官方无结核病（OTF）牛群中进行的所有常规测试的日期、地点和皮褶测量数据，按照与已知感染（OTF-退出）牛群的距离（按距离和时间）分离情况，估算了SICCT试验在三个临界值下的特异性。当测试牛群与最近感染牛群的距离超过8公里时，检测呈阳性的动物比例保持恒定（P>0.20）。对于标准临界值，计算出的特异性为99.98%（95%置信区间±0.004%），相当于每检测5000头未感染动物会出现1例假阳性结果。对于严格临界值，特异性为99.91%（±0.013%），对于超严格临界值（选择所有反应动物和不确定反应动物），特异性为99.87%（±0.017%）。该试验的估计阳性预测值平均为91%，并因地区患病率而异。本研究进一步证明了在英国条件下SICCT试验具有高特异性，表明目前在英国使用该试验扑杀的牛中超过90%已被感染，并支持至少对这些牛进行扑杀以控制牛结核病。
