OBJECTIVES: Given that more than 1 million people annually develop isoniazid-resistant tuberculosis (Hr-TB), the issue of Hr-TB may go unnoticed. However, limited studies have focused on the clinical treatment of Hr-TB in China, particularly regarding treatment outcomes and influencing factors. This study aimed to evaluate the treatment outcomes of Hr-TB patients in Shanghai from 2018 to 2021 and analyze the influencing factors, including demographic characteristics, clinical features, and treatment-related factors. METHODS: This study retrospectively reviewed the medical records of Hr-TB patients registered in the TB management information system (TBMIS) from 2018 to 2021. Differences in demographic characteristics, clinical information, and treatment outcomes were evaluated. Multivariable logistic regression was used to identify risk factors associated with unfavorable outcomes. RESULTS: A total of 664 patients with Hr-TB were included in the analysis. 84 cases (12.7%) had unfavorable outcomes. Only 318 (47.9%) Hr-TB patients used regimens containing fluoroquinolones (FQs). Adverse events occurred in 127 cases (19.1%), of which 12 cases (1.81%) discontinued treatment due to adverse events. There was statistically significant difference in the occurrence of adverse events between the different treatment regimens (P<
0.002). Multivariable logistic regression showed that older age (aOR=6.13, 95%CI=1.24-30.24, p=0.026), use of injectable agents (aOR=3.75, 95%CI=1.29-10.94, p=0.016), and treatment duration (95%CI=21.85-1487.61, p<
0.002) were risk factors for unfavorable treatment outcomes. CONCLUSION: Unfavorable outcomes were more frequent among older patients and those receiving injectable agents among Hr-TB patients in Shanghai, a low-endemic region for TB. This emphasizes the need for timely diagnosis and optimized treatment strategies for isoniazid-resistant tuberculosis.