Abstract
Brucellosis is a serious infectious disease that causes significant economic losses in the livestock industry. Its early diagnosis allows an adequate disease control in cattle. DAVIH Laboratories designed a lateral flow immunochromatographic assay using protein A-colloidal gold as a detector reagent (LFIA-PA). The objective of this work was to compare the performance of this assay using protein G-colloidal gold (LFIA-PG) with its performance using protein A-colloidal gold as the detector reagent. The assays were carried out with 20 μL of serum and 130 μL of running buffer. Interpretation of bands was by visual inspection with the naked eye at 15- 20 minutes after sample application. The tests were evaluated with 449 samples of bovine serum (111 positive and 338 negative). The diagnostic sensitivity and specificity, the positive and negative predictive values, and the efficacy of both assays were calculated, and their concordance was estimated by calculating the kappa (k) index. The estimated values of the parameters for LFIA-PG and LFPIA-PA were 100 % and 95.2 % of diagnostic sensitivity, 96.2 % and 97.3 % of diagnostic specificity, 89.5 % and 92.3 % for the positive predictive value, 100 % and 98.5 % for the negative predictive value, and 97.1 % and 96,89 % of efficacy, respectively. The concordance between both tests was very good (k = 0.95). It was shown the possibilities of developing a system with LFIA-PG capable of detecting antibodies against Brucella spp. The performance of the test makes possible its use as a screening method in the diagnosis of brucellosis.

Key words: Brucellosis, diagnosis, bovine, rapid immunochromatographic test, Brucella spp.