BackgroundActive pulmonary tuberculosis (TB) is associated with intra-hospital spread of the disease. Expeditious diagnosis and isolation are critical for infection control. However, factors that lead to delayed isolation of smear-positive pulmonary TB patients, especially among the elderly, have not been reported. The purpose of this study is to investigate factors associated with delay in the isolation of smear-positive TB patients.MethodsAll patients with smear-positive pulmonary TB admitted between January 2008 and December 2016 were included. The setting was a Japanese acute care teaching hospital. Following univariate analysis, significant factors in the model were analyzed using the multivariate Cox proportional hazard model.ResultsSixty-nine patients with mean age of 81 years were included. The median day to the isolation of pulmonary TB was 1 day with interquartile range, 1–4 days. On univariate analysis, the time to isolation was significantly delayed in male patients (p = 0.009), in patient who had prior treatment with newer quinolone antibiotics (p = 0.027), in patients who did not have chronic cough (p = 0.023), in patients who did not have appetite loss (p = 0.037), and in patients with non-cavitary lesion (p = 0.005), lesion located other than in the upper zone (p = 0.015), and non-disseminated lesion on the chest radiograph (p = 0.028). On multivariate analysis, the time to isolation was significantly delayed in male patients (hazard ratio [HR], 0.47; 95% confidence interval [CI], 0.25 to 0.89; P = 0.02), in patients who did not have chronic chough (HR, 0.52; 95% CI, 0.28 to 0.95; P = 0.033), and in patients with non-cavitary lesion on the chest radiograph (HR, 0.46; 95% CI, 0.23 to 0.92; P = 0.028).ConclusionsIn acute care hospitals of an aging society, prompt diagnosis and isolation of TB patients are important for the protection of other patients and healthcare providers. Delay in isolation is associated with male gender, absence of chronic cough, and presence of non-cavitary lesions on the chest radiograph.