TABLE 1.

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

iELISAGroupsaCutoff (RI)dSensitivity (95% CI)Specificity (95% CI)LR+eLR−e
Anti-IgG-HRPObGI × GII5682.9 (71.4-94.4)82.3 (73.9-90.7)4.70.274
GI × GIII4097.6 (92.8-102.3)97.1 (93.9-100.3)33.70.025
GI × GIV4987.8 (77.8-97.8)89.2 (85.6-92.9)8.10.137
Protein A-HRPOcGI × GII3880.5 (68.4-92.6)94.9 (90.1-99.8)15.80.205
GI × GIII2097.6 (92.8-102.3)97.1 (94.0-100.3)33.70.025
GI × GIV2297.6 (92.8-102.3)94.6 (91.9-97.3)18.10.025
  • a GI, 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).

  • b iELISA using anti-bovine IgG labeled with peroxidase (HRPO) as conjugate.

  • c iELISA using protein A-HRPO as conjugate.

  • d Reactivity index (RI) = (mean OD sample/mean OD positive control) × 100.

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