Risk factors for recurrent tuberculosis after successful treatment in a high burden setting: a cohort study
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RESEARCH ARTICLE
Open Access
Risk factors for recurrent tuberculosis after successful treatment in a high burden setting: a cohort study Patrick George Tobias Cudahy1,2* , Douglas Wilson2* and Ted Cohen3
Abstract Background: People successfully completing treatment for tuberculosis remain at elevated risk for recurrent disease, either from relapse or reinfection. Identifying risk factors for recurrent tuberculosis may help target posttuberculosis screening and care. Methods: We enrolled 500 patients with smear-positive pulmonary tuberculosis in South Africa and collected baseline data on demographics, clinical presentation and sputum mycobacterial cultures for 24-loci mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing. We used routinely-collected administrative data to identify recurrent episodes of tuberculosis occurring over a median of six years after successful treatment completion. Results: Of 500 patients initially enrolled, 333 (79%) successfully completed treatment for tuberculosis. During the follow-up period 35 patients with successful treatment (11%) experienced a bacteriologically confirmed tuberculosis recurrence. In our Cox proportional hazards model, a 3+ AFB sputum smear grade was significantly associated with recurrent tuberculosis with a hazard ratio of 3.33 (95% CI 1.44–7.7). The presence of polyclonal M. tuberculosis infection at baseline had a hazard ratio for recurrence of 1.96 (95% CI 0.86–4.48). Conclusion: Our results indicate that AFB smear grade is independently associated with tuberculosis recurrence after successful treatment for an initial episode while the association between polyclonal M. tuberculosis infection and increased risk of recurrence appears possible. Keywords: Mixed-infection, South Africa, Relapse, Reinfection, Fuzzy match
Introduction Patients who have recently completed treatment for tuberculosis (TB) are at elevated risk of recurrent TB disease, either as a result of relapse or reinfection [1, 2]. When individuals are diagnosed with recurrent TB, they are less likely to complete treatment and suffer higher * Correspondence: [email protected]; [email protected] 1 Section of Infectious Disease, Department of Medicine, Yale University School of Medicine, New Haven, CT, USA 2 Department of Internal Medicine, Edendale Hospital, University of KwaZulu-Natal, 5th Floor, Private Bag X 509, Plessislaer, KZN, Pietermaritzburg 3216, South Africa Full list of author information is available at the end of the article
mortality than those with first episodes of TB [3]. While there is a growing appreciation of the risks associated with recurrent TB, a clearer picture of which covariates place individuals at greater risk of recurrent disease can inform more targeted post-tuberculosis care and monitoring. Several covariates have been found to be associated with recurrence of TB after completion of treatment. Drug-resistance [4], smoking [5], HIV infection with low CD4 lymphocyte counts [6], substance use [7], chronic lung disease [8]
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