Improved Early Detection of Focal Brucellosis Complications with Anti-Brucella IgG.

To evaluate the associations of inflammatory factors and serological test results with complicated brucellosis, we recruited 285 patients with a diagnosis of brucellosis between May 2016 and September 2019. The patients were subsequently classified into two groups according to the presence of complications. We collected demographic and clinical information and routine laboratory test results in addition to anti-Brucella IgG and IgM levels. Anti-Brucella IgG and IgM were uniformly tested using enzyme-linked immunosorbent assays (ELISAs) in this study. Among the 285 patients with brucellosis, 111 (38.95%) had complicated brucellosis. Osteoarthritis occurred more often in the subacute and chronic stages than in the acute stage (P = 0.002). Genital infection occurred more frequently in the acute stage than in the other stages (P = 0.023). Fever was not frequently observed in complicated cases (P < 0.001). The erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) and anti-Brucella IgM and IgG levels were higher in complicated-brucellosis patients than in uncomplicated-brucellosis patients (P < 0.001). Anti-Brucella IgG, with an area under the curve of 0.885 (95% confidence interval [CI], 0.847 to 0.924), was the most robust indicator of complicated brucellosis. Positive culture, anti-Brucella IgM, the ESR, and CRP could be considered indicators, but their efficacy was weaker than that of IgG. In conclusion, a high ESR, high CRP, high anti-Brucella IgM and IgG levels, and positive culture were indicators of complicated brucellosis; among these, anti-Brucella IgG was the most robust biomarker.