Nielsen Søren S, Grønbaek Carsten, Agger Jens F, Houe Hans
Department of Animal Science and Animal Health, The Royal Veterinary and Agricultural University, Grønnegårdsvej 8, DK-1870 C, Frederiksberg, Denmark.
Prev Vet Med. 2002 Mar 14;53(3):191-204. doi: 10.1016/s0167-5877(01)00280-x.
The accuracy of three diagnostic tests for paratuberculosis was evaluated using maximum-likelihood estimation of sensitivity and specificity. We also explored the variety of estimates that can be obtained if the tests are to be used in populations of different composition with regard to infection and disease states. Two enzyme-linked immunosorbent assays (ELISAs) were evaluated separately with the faecal culture (FC). The study was carried out as a cross-sectional field study to cover all likely states of infection with Mycobacterium avium subsp. paratuberculosis.The three basic assumptions for the maximum-likelihood technique were evaluated to validate the results. Our accuracy estimates for the ELISAs were not very different from those previously published, but those for faecal culture differed if a different cut-off value was chosen for the ELISA. If faecal culture was used for screening in a Danish dairy region where the median ELISA reading was a measure of the general disease situation, the sensitivity of the faecal culture was 20-25%. If faecal culture was used as a confirmatory test on cows with a high ELISA reading (and thus high level of antibodies), the sensitivity of the faecal culture would be in the range 60-70%. These results emphasise the importance of the composition of a target population before selecting a specific diagnostic test for a given purpose. We concluded that faecal culture is useful for confirmation but not for screening purposes.
使用敏感性和特异性的最大似然估计法评估了三种副结核病诊断检测的准确性。我们还探讨了如果这些检测应用于感染和疾病状态构成不同的人群时所能获得的各种估计值。分别用两种酶联免疫吸附测定法（ELISA）与粪便培养法（FC）进行评估。该研究作为一项横断面现场研究开展，以涵盖鸟分枝杆菌副结核亚种所有可能的感染状态。对最大似然技术的三个基本假设进行了评估以验证结果。我们对ELISA的准确性估计与之前发表的结果差异不大，但如果为ELISA选择不同的临界值，粪便培养法的准确性估计则有所不同。如果在丹麦一个奶牛养殖区使用粪便培养法进行筛查，其中ELISA读数中位数可衡量总体疾病情况，那么粪便培养法的敏感性为20% - 25%。如果将粪便培养法用作ELISA读数高（即抗体水平高）的奶牛的确诊检测，那么粪便培养法的敏感性将在60% - 70%的范围内。这些结果强调了在为特定目的选择特定诊断检测之前，目标人群构成的重要性。我们得出结论，粪便培养法有助于确诊，但不适合用于筛查目的。
