Abstract

Background: Previously treated Tuberculosis (TB) cases account for ~7%-8% of incident TB globally and in Singapore. Molecular fingerprinting has enabled the differentiation of these patients into relapsed or re-infection cases.

Methods: Patient demographics, disease characteristics and treatment information were obtained from the national TB notification registry and TB Control Unit. We performed a retrospective, case-control study to evaluate factors associated with recurrent TB disease in Singapore citizens and Permanent Residents with culture-positive TB from 2006 to 2013 and who developed a second episode of culture-positive TB up to 2016 using multivariable logistic regression analyses.

Results: 91 cases with culture-positive first and recurrent TB disease episodes were notified during the study period. Available DNA fingerprinting results for both episodes in 49 cases differentiated these into 28 relapsed and 21 re-infection cases. Recurrent TB was associated with age ≥ 60 years (adjusted odds ratio [aOR] 2.06, 95% confidence interval [CI] 1.14–3.73), male gender (aOR 2.29, 95% CI 1.23–4.43) and having concomitant pulmonary and extrapulmonary TB (aOR 2.76, 95% CI 1.43–5.36); and was less likely in persons of non-Malay ethnicity (aOR 0.50, 95% CI 0.26–0.95). Relapse was associated with having concomitant pulmonary and extrapulmonary TB (aOR 8.24, 95% CI 2.28–36.35), and sputum acid fast bacilli smear positivity (aOR 3.59, 95% CI 1.27–11.32).

Conclusion: Relapse and re-infection contributed to 57% and 43% respectively of recurrent TB in Singapore. Our study identified the hitherto unrecognized association of concomitant pulmonary and extrapulmonary TB disease with risk of relapse.

Keywords: Tuberculosis, Relapse, Exogeneous reinfection Extrapulmonary