title: Factors Affecting Time to Sputum Culture Conversion in Adults with Pulmonary Tuberculosis: A Historical Cohort Study without Censored Cases.
abstract: BACKGROUND
  In patients with pulmonary tuberculosis (TB), shortening the time to sputum culture conversion is desirable to reduce the likelihood of mycobacterial transmission. A persistent positive sputum culture after 2 months of treatment is reported to be associated with the presence of cavitation and the extent of disease on chest X-ray, high colony count, diabetes mellitus, and smoking. However, little is known about factors affecting the time to sputum culture conversion. This study was conducted to evaluate factors affecting the time to sputum culture conversion throughout the course of treatment in adults with pulmonary TB.
  
  
  METHODS
  This study was performed using a database of the medical records of patients with active pulmonary TB who were treated at Hirakata Kohsai Hospital in Hirakata City, Osaka, Japan, from October 2000 to October 2002. Cox proportional-hazards analysis was used to evaluate factors affecting the time to sputum culture conversion after adjusting for potential confounders.
  
  
  RESULTS
  The data of 86 patients with pulmonary TB were analyzed. The median time to sputum culture conversion was 39 days, and the maximum time was 116 days. The Cox proportional-hazards analysis showed that a higher smear grading (HR, 0.40; 95%CI, 0.23-0.71) and a history of ever smoking (HR, 0.48; 95%CI, 0.25-0.94) were associated with delayed sputum culture conversion.
  
  
  CONCLUSIONS
  High smear grading and smoking prolonged the time to sputum culture conversion in adults with pulmonary TB. To effectively control TB, measures to decrease the cigarette smoking rate should be implemented, in addition to early detection and timely anti-TB treatment.
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Kanda
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Taishi
authors.initials: T
authors.lastname: Nagao
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Nguyen Van
authors.initials: NV
authors.lastname: Tho
authors.affiliation: Health Administration Center, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Ogawa
authors.affiliation: Department of Medical Statistics, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Murakami
authors.affiliation: Division of Infection Control and Prevention, Shiga University of Medical Science Hospital, Shiga, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Osawa
authors.affiliation: Department of Radiology, Hirakata Kohsai Hospital, Osaka, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Saika
authors.affiliation: Department of Radiology, Morinomiya Hospital, Osaka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Doi
authors.affiliation: Division of Respiratory Medicine, Department of Medicine, Shiga University of Medical Science, Shiga, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Nakano
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000627:therapeutic use; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D007564:Japan; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D013183:Sputum / Q000382:microbiology*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000188:drug therapy / Q000401:mortality
chemical_list: D000995:Antitubercular Agents