Predictors of sputum culture conversion among patients with tuberculosis in the era of tuberculosis resurgence

Background: Sputum culture conversion among patients with tuberculosis (TB) is the most important indicator for the effectiveness of treatment and the infectivity of the disease. We sought to investigate predictors for documented sputum culture conversion among TB cases reported in the surveillance system. Methods: This study included 780 patients with pulmonary TB who were initially sputum culture positive in New Jersey in 1994-1995. These patients were followed up for at least 1 week and up to 1 year. Kaplan-Meier curves and Cox proportional hazards models were performed to analyze the data. Results: Overall, 469 (60.1%) of the 780 patients had documented sputum culture conversion. The elderly (36%) and non-Hispanic whites (41.3%) were the least likely to have documented sputum conversion. Patients who were initially given 4 or more drugs were 36% more likely to have documented sputum conversion than those who were initially given fewer than 4 drugs, after adjusting for other factors. Patients who were under the care of chest clinics and the model TB center were about 3 times more likely to have documented sputum conversion than those under care of private physicians. Sex, recurrent TB, foreign-born status, homelessness, injecting drug use, human immunodeficiency virus infection and drug-resistant TB were not significantly associated with the documentation of sputum culture conversion. Conclusions: A substantial proportion of sputum culture-positive TB patients have no documented sputum culture conversion. The type of care provider was the predominant determinant for the documentation of sputum culture conversion.