Objective To understand the incidence of relapse of pulmonary tuberculosis (TB) and the possible influencing factors in Nantong, Jiangsu Province, from 2013 to 2020, and provide reference for further improvement of the prevention and control strategies of pulmonary TB in Nantong.

Methods A retrospective cohort study was conducted, the medical record information of active pulmonary TB patients registered in Nantong from 2013 to 2021were collected from National Tuberculosis Management Information System for the analysis combined with the incidence data of relapse of pulmonary TB from 2014 to 2021, and the annual incidence rate of the relapse and the cumulative incidence rate of the relapse in n years were calculated by using the life table method. Cox proportional hazards regression model was used to analyze the influencing factors associated with the relapse of pulmonary TB.

Results In the 19176 successfully treated pulmonary TB patients included in the study, a total of 906 (4.72%) relapse cases were observed at the end of the observation, with the incidence rate of 0.99/100 person years and within a median time of 1.25 (0.58, 2.58) years. In the relapse cases, 42.49% occurred within 1 year after successful treatment, 80.79% occurred within 3 years after successful treatment, and 93.27% occurred within 5 years after successful treatment. Multivariate Cox regression analysis showed that being man hazard ratio(HR)=1.53, 95% confidence interval (CI): 1.30−1.80, P<0.001, being farmer (HR=3.04, 95%CI: 2.30−4.01, P<0.001), being positive in etiological test (HR=1.53, 95%CI: 1.23−1.89, P<0.001), being positive in sputum smear test at the end of month 2 (HR=1.52, 95%CI: 1.02−2.27, P=0.039), being diabetes patients (HR=3.54, 95%CI: 2.48−5.06, P<0.001) were the independent risk factors for the relapse of pulmonary TB. Age 20−39 years (HR=0.60, 95%CI: 0.36−1.00, P=0.048), medical care seeking due to symptom (HR=0.68, 95%CI: 0.57−0.80, P<0.001), and comprehensive management (HR=0.68, 95%CI: 0.55−0.84, P<0.001) were protective factors for the relapse of pulmonary TB.

Conclusion The incidence rate of relapse of pulmonary TB within 5 years after successful treatment was relatively high in Nantong, and regular follow-up should be strengthened for the newly treated pulmonary TB patients after drug withdrawal, especially within 5 years after successful treatment; During the treatment process, it is necessary to strengthen the monitoring of blood glucose level, sputum bacteria and drug resistance of newly treated pulmonary TB patients complicated with diabetes, those with positive etiological results and those with positive sputum test results at the end of month 2, and timely adjust the treatment plan according to the patient's will and clinical condition to reduce the relapse of pulmonary TB in high-risk groups.