Large-Scale Evaluation of IgM and IgG Lateral Flow Assays for Rapid Diagnosis of Human Brucellosis

Background: Human brucellosis is a major occupational hazard in India, especially among veterinary healthcare workers due to frequent contact with livestock. This study evaluated in-house standardized IgM and IgG-based lateral flow assays (LFAs) against a Rose Bengal Plate Test (RBPT) and a Serum Agglutination Test (SAT). Methods: A total of 1356 serum samples (392 veterinary doctors and 964 paraveterinary staff) were sourced for evaluation of the tests across Karnataka, India. The results were analyzed for performance metrics {DSe (Diagnostic Sensitivity), DSp (Diagnostic Specificity), PPV (Positive Predictive Value), NPV (Negative Predictive Value), accuracy, and kappa with 95% CI} through chi-square and regression analyses. Results: Overall seropositivity was 7.67% (104/1356; 95% CI: 6.31–9.22) by RBPT, 3.47% (47/1356; 95% CI: 2.56–4.58) by SAT, 2.95% (40/1356; 95% CI: 2.12–4.00) by IgM_LFA, and 6.34% (86/1356; 95% CI: 5.10–7.77) by IgG_LFA. The RBPT vs. IgM and IgG_LFA showed a DSe of 85.3% (74.6–92.7) and 82.69% (74.03–89.41), respectively. Compared with SAT, IgM_LFA and IgG_LFA demonstrated high DSe values of 95.35% (84.2–99.4) and 96.55% (88.1–99.6), respectively. Seroprevalence was higher among paraveterinary staff (8.71%, CI 95%: 7.20–10.90) than veterinary doctors (5.10%, CI 95%: 3.14–7.77), higher in males (8.30%, CI 95%: 6.77–10.04) than females (4.02%, CI 95%: 2.44–9.05) and higher in individuals aged >55 years (9.09%, CI 95%: 5.64–13.69) compared to other age groups. Regression analysis yielded coefficients of 62.90% (p = 0.0107) for veterinarians and 87.89% (p = 0.0001) for paraveterinarians. Conclusions: This integrated field evaluation confirms improvement in brucellosis detection and emphasizes the need for field-applicable diagnostic tools.