<![CDATA[Background: Brucellosis, a zoonotic disease caused by bacteria of the genus Brucella, affects multiple animal species worldwide. Timely detection and control depend critically on rapid diagnostic tests. Purpose: This study evaluated the diagnostic performance of two rapid lateral flow tests based on similar principles but employing different conjugates (protein A colloidal gold and protein G colloidal gold) for detecting antibodies against Brucella spp. in various animal species. Method: Across laboratory and field conditions in Cuba, 1,394 blood and serum samples from cattle, swine, sheep, and buffalo were analyzed. As the reference standard, complement fixation reaction (CFR) served as the benchmark. The calculated parameters included sensitivity, specificity, predictive values, Kappa index, and chi-square statistics. Results: Adequate diagnostic performance, with values exceeding 90% in most cases. The protein G colloidal gold conjugate exhibited superior overall performance: sensitivity of 98.1% (95% CI: 96.8–99.0%), specificity of 94.5% (95% CI: 92.8–95.9%), and Kappa index of 0.95 (95% CI: 0.93–0.97), denoting very good agreement with CFR. For cattle under field conditions, protein G achieved 100% sensitivity (95% CI: 98.3–100%), whereas protein A yielded 95.7% (95% CI: 92.1–97.9%). Lower specificity (84.4–85.0%) was recorded in swine, possibly attributable to Brucella suis circulation and the use of B. abortus antigen. Statistically significant associations between rapid tests and CFR across all species evaluated (p < 0.001) were confirmed by chi-square analysis. Conclusion: Both rapid tests, particularly the colloidal gold protein G conjugate, are reliable and practical tools for diagnosing brucellosis in multiple animal species. Implementing these tests could strengthen surveillance and control programs in Cuba, contributing to the One Health approach.]]>
