title: Assessment of defined antigens for the diagnosis of bovine tuberculosis in skin test-reactor cattle.
abstract: The continued use of purified protein derivative (PPD) tuberculin is considered to be the main factor which limits the specificity of diagnostic tests for bovine tuberculosis (TB). This study evaluated a whole blood interferon-gamma (IFN-gamma) assay and compared the diagnostic potential of PPD with two tuberculosis-specific antigens, ESAT-6 and MPB70. To provide estimates of sensitivity and specificity, responses were measured in 180 skin test-reacting cattle, of which 131 were confirmed as tuberculous, and in 128 cattle from TB-free herds. For the skin test reactors, there was a positive correlation between the IFN-gamma responses to PPD from Mycobacterium bovis (PPDB) and PPD from Mycobacterium avium (PPDA), indicating cross-reactivity between these complex antigens which are the basis of the skin test. In comparisons of the ESAT-6 IFN-gamma test with a PPD IFN-gamma test (using PPDB compared with PPDA), there was a decrease in sensitivity (76.3 per cent vs 89.3 per cent), but a clear increase in specificity (99.2 per cent vs 92.2 per cent). The provision of high specificity, even with lower sensitivity, offers major benefits for testing in areas with a low incidence of TB.
authors.affiliation: Department of Agriculture for Northern Ireland, Belfast.
authors.forename: J M
authors.initials: JM
authors.lastname: Pollock
authors.forename: R M
authors.initials: RM
authors.lastname: Girvin
authors.forename: K A
authors.initials: KA
authors.lastname: Lightbody
authors.forename: R A
authors.initials: RA
authors.lastname: Clements
authors.forename: S D
authors.initials: SD
authors.lastname: Neill
authors.forename: B M
authors.initials: BM
authors.lastname: Buddle
authors.forename: P
authors.initials: P
authors.lastname: Andersen
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000097:blood*; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D007371:Interferon-gamma / Q000097:blood; D009162:Mycobacterium avium / Q000276:immunology* / Q000302:isolation & purification; D009163:Mycobacterium bovis / Q000276:immunology* / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D014374:Tuberculin Test / Q000662:veterinary*; D014380:Tuberculosis, Bovine / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D000942:Antigens, Bacterial; D007371:Interferon-gamma