Risk factors for sputum-smear positive in active tuberculosis patients

<bold>Background:</bold> Sputum smear positive is one of the main criteria to judge the infectivity of tuberculosis patients. Therefore, early identification of active TB population with sputum smear positive is necessary for timely detection and proper management of tuberculosis infection source. This study analyzed the clinical characteristics and risk factors of sputum smear-positive patients with active tuberculosis in southwest China, and provided guidance for clinical practice. <bold>Methods:</bold> A total of 7401 patients diagnosed with active tuberculosis with sputum smear results at West China Hospital of Sichuan University were retrospectively included. Of these, 6332 were negative and 1069 were positive at first diagnosis. Baseline data, and routine blood and biochemical indices were compared between the two groups. Logistic regression was used to investigate the risk factors for sputum smear-positivity in active tuberculosis. <bold>Results:</bold> Multivariate logistic regression analysis showed that low BMI(OR:0.87; 95%CI:0.86, 0.89;p=0.001), alcohol consumption(OR:1.67; 95%CI:1.37,2.03;p=0.001), smoking history(OR:1.27; 95%CI:1.09,1.48;p=0.002), high blood glucose level(OR:1.14; 95%CI:1.06, 1.33;p=0.047), diabetes mellitus(OR:1.95; 95%CI:1.61, 2.35;p=0.001) and solid organ malignancy or lymphoma(OR:1.61; 95%CI:1.18, 2.21;p=0.003) were risk factors for positive sputum smear at initial diagnosis of active tuberculosis. <bold>Conclusions:</bold> Low BMI, a history of alcohol consumption, smoking, elevated blood glucose level, diabetes, and a history of tumor were risk factors for positive sputum smears in active tuberculosis.