Recurrent tuberculosis (TB) continues to be a significant problem and is an important indicator of the effectiveness of TB control. Recurrence can occur by relapse or exogenous reinfection. Recurrence of TB is still a major problem in high-burden countries, where there is lack of resources and no special attention is being given to this issue. The rate of recurrence is highly variable and has been estimated to range from 4.9% to 47%. This variability is related to differences in regional epidemiology of recurrence and differences in the definitions used by the TB control programs. In addition to treatment failure from noncompliance, there are several key host factors that are associated with high rates of recurrence. The widely recognized host factors independent of treatment program that predispose to TB recurrence include gender differences, malnutrition; comorbidities such as diabetes, renal failure, and systemic diseases, especially immunosuppressive states such as human immunodeficiency virus; substance abuse; and environmental exposures such as silicosis. With improved understanding of the human genome, proteome, and metabolome, additional host-specific factors that predispose to recurrence are being identified. Information on temporal and geographical trends of TB cases as well as studies with whole-genome sequencing might provide further information to enable us to fully understand TB recurrence and discriminate between reactivation and new infection. The recently launched World Health Organization End TB Strategy emphasizes the importance of integrated, patient-centered TB care. Continued improvement in diagnosis, treatment approaches, and an understanding of host-specific factors are needed to fully understand the clinical epidemiological and social determinants of TB recurrence.

Recurrent tuberculosis (TB), defined as TB that recurs after a patient has been considered cured, constitutes a challenge to TB control. In low TB burden countries, the underlying causes and consequences of recurrent TB are poorly understood. We conducted a literature review to summarise the evidence of recurrent TB in low-burden settings and to address current gaps in knowledge. We included peer-reviewed publications on studies conducted in countries with an estimated TB incidence of <100 cases per 100 000 population. The Newcastle-Ottawa scale was used to assess study quality. The review yielded 44 manuscripts, 39 of which were reports of observational studies and 5 of clinical trials. The median percentage of TB patients experiencing an episode of recurrent TB after treatment completion was 3.4% (interquartile range [IQR] 1.6-6.0, range 0.4-16.7) in studies with a median follow-up of 7.8 years (IQR 5-12, range 2-33). The median percentage of recurrences attributable to endogenous reactivation (rather than exogenous reinfection) was 81% (IQR 73.1-85.5, range 49-100). Commonly identified risk factors for recurrence in low-burden settings included infection by the human immunodeficiency virus, low socio-economic status, foreign birth and infection with drug-resistant TB. Current understanding of recurrence in low-burden settings is limited, in part due to substantial methodological differences between studies. Further research is required to delineate the mechanisms of TB recurrence, its health and clinical impact, as well as the implications for TB elimination efforts in low-burden countries.

Patients completing treatment for tuberculosis (TB) in high-prevalence settings face a risk of developing recurrent disease. This has important consequences for public health, given its association with drug resistance and a poor prognosis. Previous research has implicated individual factors such as smoking, alcohol use, HIV, poor treatment adherence, and drug resistant disease as risk factors for recurrence. However, little is known about how these factors co-act to produce recurrent disease. Furthermore, perhaps factors related to the index disease means higher burden/low resource settings may be more prone to recurrent disease that could be preventable.We conducted a case-control study nested within a cohort of consecutively enrolled adults who were being treated for smear positive pulmonary TB in 70 randomly selected district clinics in Vietnam. Cases were patients with recurrent TB, identified by follow-up from the parent cohort study. Controls were selected from the cohort by random sampling. Information on demographic, clinical and disease-related characteristics was obtained by interview. Treatment information was extracted from clinic registries. Logistic regression, with stepwise selection, was used to develop a fully adjusted model for the odds of recurrence of TB.We recruited 10,964 patients between October 2010 and July 2013. Median follow-up was 988 days. At the end of follow-up, 505 patients (4.7%) with recurrence were identified as cases and 630 other patients were randomly selected as controls. Predictors of recurrence included multidrug-resistant (MDR)-TB (adjusted odds ratio 79.6; 95% CI: 25.1-252.0), self-reported prior TB therapy (aOR=2.5; 95% CI: 1.7-3.5), and incomplete adherence (aOR=1.9; 95% CI 1.1-3.1).Index disease treatment history is a leading determinant of relapse among patients with TB in Vietnam. Further research is required to identify interventions that will reduce the risk of recurrent disease and enhance its early detection within high-risk populations.Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Studying the recurrence of smear-positive pulmonary tuberculosis (TB) is a convenient way to evaluate the effectiveness of TB control programs and identify vulnerable patients. In the present study, the rate of recurrence of TB and its predictors were determined in Iran.This study was a retrospective cohort. Eligible people were patients with smear-positive TB who were diagnosed from 2002 to 2011. The end of the follow-up time was December 2013. The number of people who entered the cohort was 1,271 subjects. In order to determine the predictors of recurrence, multivariate logistic regression was used. Analysis was done using SPSS 20.The recurrence incidence was 8.3% and in 85.9% of these patients, it occurred in the time interval of 1-5 years after successful treatment. The recurrence rate was not significantly related to gender, age group, and diabetes. But it was significantly higher in patients whose sputum smear grading before treatment was 2 + or more, patients with positive sputum smear at the end of the second month of the treatment, patients who had completed treatment, and patients who were smokers (P < 0.05).Our study showed that a considerable percentage of smear-positive pulmonary TB patients experience recurrence and that some patients are at a higher risk of recurrence.