Specificity of the comparative skin test for bovine tuberculosis in Great Britain.
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Great Britain (GB) between 2002 and 2008, according to their separation (by distance and time) from known infected (OTF-withdrawn) herds.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.
Department of Epidemiological Sciences, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone KT15 3NB, UK.
A V
AV
Goodchild
Department of Epidemiological Sciences, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone KT15 3NB, UK.
S H
SH
Downs
Data Sciences Group, Animal and Plant Health Agency (APHA), Woodham Lane, Addlestone KT15 3NB, UK.
P
P
Upton
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.
J L N
http://orcid.org/0000-0002-0258-3188
JL
Wood
Veterinary and Science Policy Advice Team of APHA and Bovine Tuberculosis Programme of Defra, Nobel House, 17 Smith Square, London SW1P 3JR, UK.
R
R
de la Rua-Domenech
D000818:Animals; D002417:Cattle; D011159:Population Surveillance / Q000379:methods; D012680:Sensitivity and Specificity; D014374:Tuberculin Test / Q000379:methods / Q000662:veterinary*; D014380:Tuberculosis, Bovine / Q000175:diagnosis* / Q000453:epidemiology; D006113:United Kingdom / Q000453:epidemiology
Bovine tuberculosis; Cattle; Comparative Tuberculin Skin Test; Diagnostics; Great Britain; Specificity