TABLE 1.

Threshold values (cutoff) relative to iELISA for IgG antibodies to Brucella abortus in bovine serum samples from different groups

iELISA	Groupsa	Cutoff (RI)d	Sensitivity (95% CI)	Specificity (95% CI)	LR+e	LR−e
Anti-IgG-HRPOb	GI × GII	56	82.9 (71.4-94.4)	82.3 (73.9-90.7)	4.7	0.274
	GI × GIII	40	97.6 (92.8-102.3)	97.1 (93.9-100.3)	33.7	0.025
	GI × GIV	49	87.8 (77.8-97.8)	89.2 (85.6-92.9)	8.1	0.137
Protein A-HRPOc	GI × GII	38	80.5 (68.4-92.6)	94.9 (90.1-99.8)	15.8	0.205
	GI × GIII	20	97.6 (92.8-102.3)	97.1 (94.0-100.3)	33.7	0.025
	GI × GIV	22	97.6 (92.8-102.3)	94.6 (91.9-97.3)	18.1	0.025

^aGI, nonvaccinated seropositive cows originated from areas where Brucella is endemic or an outbreak is occurring (n = 41); GII, S19-vaccinated heifers between 3 and 8 months of age, originated from areas where Brucella is endemic, and serum samples were analyzed at 3 months postvaccination (n = 79); GIII, S19-vaccinated cows between 3 and 8 months of age, originated from areas where Brucella is endemic, and serum samples were analyzed after 24 months of age (n = 105); GIV, nonvaccinated seronegative cows originated from areas where Brucella is nonendemic (n = 278).

^biELISA using anti-bovine IgG labeled with peroxidase (HRPO) as conjugate.

^ciELISA using protein A-HRPO as conjugate.

^dReactivity index (RI) = (mean OD sample/mean OD positive control) × 100.

^eLR+, positive likelihood ratio; LR−, negative likelihood ratio. The figures in bold indicate significant LR values.