Determining Factors Affecting Time to Sputum Smear Conversion in Pulmonary Tuberculosis Patients Using Cox Semi-Parametric Method

Background & Aims: Tuberculosis is one of the most important diseases of century that involves all the human organs including lungs. Due to the yearly occurrence of 9 millions new cases and 1.5 millions deaths in the world, tuberculosis is in the center of attention. The aim of this study was to indentify factors affecting the time required for sputum smear conversion in patients. Methods: This historical cohort study was performed on tuberculosis patients with pulmonary involvement and positive smear referred to Health Centers of Mashhad University of Medical Sciences from September 2012 to July 2014. The demographic characteristic of patients and features of disease were used as variables. Log Rank test, Kaplan-Meier method and Cox regression were used to analyze data (α