Comparison of laboratory methods for the diagnosis of different clinical forms of brucellosis

Brucellosis is a zoonotic infection characterized by variable clinical manifestations, a variety of transmission routes, chronic inflammation, and risk of disability. Brucellosis remains a problem of practical healthcare in Russia, especially in endemic regions. Laboratory tests for brucellosis diagnosis are rarely used together, which prevents objective comparison of their effectiveness for different clinical forms of the disease. In this study, we analyzed different laboratory methods for comprehensive diagnosis of various clinical forms of brucellosis. Objective. To compare different laboratory methods for the diagnosis of various clinical forms of brucellosis. Materials and methods. We tested serum from 1049 individuals collected between 2005 and 2022. Samples were analyzed using agglutination reaction in tubes (Wright reaction; WR), on slides (Huddleson reaction; HR), Coombs test (CT), enzymelinked immunosorbent assay (ELISA), and real-time polymerase chain reaction (PCR) for BCSP31. We also performed retrospective analysis of 325 patient records. Of them, 110 patients (34%) had acute brucellosis, whereas 215 patients (66%) had chronic brucellosis. The control group comprised 604 individuals (with no clinical, epidemiological signs tested negative for brucellosis). Results. We analyzed 325 brucellosis patients (including 110 with acute disease, 215 with chronic disease, and 120 with no clinical manifestations) and 604 healthy controls. The sensitivity of PCR in acute and chronic disease was 94% and 32%, respectively. The specificity of PCR was 99.7%. ELISA demonstrated 92% and 86% sensitivity in acute and chronic disease, respectively, with a specificity of 98%. The negative and positive prognostic value for ELIZA and PCR were 95% and 96%, 83% and 99% respectively, suggesting similar effectiveness and accuracy of these methods. The sensitivity of traditional serological tests in acute disease was 75%, 62%, and 56.3% for RH, WR, and CT, respectively. In patients with chronic brucellosis, their sensitivity did not exceed 60%. Specificity of WR and CT was 97% in chronic disease, while it of RH dropped to 83%. Conclusion. PCR and ELISA ensured high diagnostic effectiveness and accuracy in assessing the activity of infection and diagnosis of brucellosis clinical forms, as well as in screening among vulnerable individuals. Traditional serological tests, despite their lower sensitivity, confirm acute disease and need for comprehensive laboratory diagnostics of brucellosis patients. Key words: brucellosis, diagnostic methods, enzyme-linked immunosorbent assay, polymerase chain reaction, Wright reaction, Huddleson reaction, Coombs test