Objective:To study the clinical value of serum adenosine deaminase (ADA) combined with whole blood microRNA (miR)-197-3p in the diagnosis of human brucellosis.Methods:From January 2020 to September 2023, 120 patients with brucellosis were selected from the Department of Pulmonary and Critical Care Medicine, Affiliated Hospital of Jining Medical University (referred to as this hospital) and assigned to the brucellosis group, including 89 patients in the acute stage, 19 patients in the chronic stage, and 12 patients in the latent infection. In addition, 60 healthy volunteers from the animal husbandry industry were selected as the control group from the physical examination population in this hospital during the same period; sixty critically ill patients with community-acquired pneumonia were selected from the Department of Pulmonary and Critical Care Medicine of this hospital as the infection control group. Patients in the brucellosis group and infection control group were given standardized treatment. Fasting elbow venous blood samples were collected in the morning before and after treatment in the brucellosis group and infection control group, at enrollment in the control group, and serum ADA and whole blood miR-197-3p levels were tested. Multivariate logistic regression analysis was used to study the risk factors affecting the occurrence of brucellosis. Receiver operating characteristic (ROC) curve was used to evaluate the diagnostic efficacy of ADA, miR-197-3p, and their combination for brucellosis.Results:Before treatment, the levels of serum ADA (U/L: 12.35 ± 2.89, 18.33 ± 4.57, 29.75 ± 6.46, 22.20 ± 4.78, 14.15 ± 3.03) and whole blood miR-197-3p (1.09 ± 0.33, 2.25 ± 0.41, 2.68 ± 0.59, 2.43 ± 0.51, 1.18 ± 0.40) in the control, infection control, acute stage, chronic stage, and latent infection groups were compared, and the differences were statistically significant ( F = 4.38, 4.02, P = 0.014, 0.019). Compared with the control group, the serum ADA and whole blood miR-197-3p levels in the other 4 groups were higher ( P < 0.05). Compared with the infection control group, the serum ADA level in the acute stage and chronic stage groups was higher, and the serum ADA level in the latent infection group was lower ( P < 0.05); the level of whole blood miR-197-3p was higher in the acute stage group, but lower in the latent infection group ( P < 0.05). Compared with before treatment, the levels of serum ADA and whole blood miR-197-3p in the infection control, acute stage and chronic stage groups were lower after treatment ( P < 0.05). Multivariate logistic regression analysis showed that increased levels of serum ADA and whole blood miR-197-3p were risk factors for brucellosis [odds ratio ( OR) = 2.235, 3.404, 95% confidence intervals ( CI): 1.491 - 3.362, 1.623 - 7.605, P < 0.001]. ROC curve results showed that serum ADA and whole blood miR-197-3p had auxiliary significance in the diagnosis of brucellosis ( P < 0.001). The area under curve (AUC) of serum ADA combined with whole blood miR-197-3p was 0.933, which was superior to the diagnostic efficacy of serum ADA and whole blood miR-197-3p alone (AUC = 0.823, 0.840). Conclusion:The combination of serum ADA and whole blood miR-197-3p has high clinical value in the diagnosis of human brucellosis, and can provide an important reference for the clinical diagnosis and efficacy evaluation of brucellosis.