Quantitative assessment of clinical signs for the detection of classical swine fever outbreaks during an epidemic.
The performance of clinical signs as a diagnostic test for the detection of classical swine fever (CSF) outbreaks during the 1997-1998 CSF epidemic in The Netherlands was evaluated by constructing and analysing a receiver operating characteristic (ROC) curve. This curve assesses the discriminating ability of a diagnostic test over a range of test signals. The cut-off values for a defined diagnostic test to detect CSF outbreaks were set by different combinations of clinical signs observed. The area under the ROC curve, which is a quantitative measure of test performance, was significantly (P<0.001) larger than the area under the random ROC curve. This indicates that clinical signs have a significantly higher performance as a diagnostic test for the detection of CSF than for flipping a coin. However, the gain in diagnostic performance compared to a random process is not as much as we would wish it to be. The optimal efficient diagnostic test combined a sensitivity of 72.7% with a specificity of 52.7%, with a combination of the following clinical signs: unsteady gait/ataxia, not eating, not reacting to antibiotic treatment, conjunctivitis, hard faecal pellets.
Elbers
A R W
AR
Epidemiology Unit, Animal Health Service, P.O. Box 9, 7400 AA Deventer, The Netherlands. a.elbers@gdvdieren.nl
Bouma
A
A
Stegeman
J A
JA
D000818:Animals; D000855:Anorexia / Q000662:veterinary; D006691:Classical Swine Fever / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D006692:Classical Swine Fever Virus; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D020234:Gait Ataxia / Q000662:veterinary; D009426:Netherlands / Q000453:epidemiology; D012372:ROC Curve; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D013552:Swine