Abstract:Abstract: OBJECTIVE To investigate the value of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metallopoteinase 1(TIMP-1) in the differential diagnosis of pulmonary tuberculosis (PTB) and community-acquired pneumonia (CAP). METHODS 156 cases of CAP children (CAP group) and 98 cases of PTB children (PTB group) who admitted to the author’s hospital from June of 2018 to March of 2021 were retrospectively collected, and the differences in serum MMP-9 and TIMP-1 levels and their ratios be⁃ tween the two groups were compared and analyzed. Receiver operating characters curve (ROC) was used to analyze the differential di⁃ agnostic value of MMP-9 and TIMP-1 levels and their ratios. RESULTS Compared with CAP group, MMP-9 and TIMP-1 levels and the ratios were significantly increased in PTB group. The differences were all significant (t=5.573, 3.362, 7.116, P＜0.05). Further correlation analysis found that MMP-9 levels were positively correlated with MMP-9/TIMP-1 (r=0.143, P=0.023), and TIMP-1 levels and MMP-9/TIMP-1 (r=-0.129, P=0.040), and the ROC area (AUC) was 0.702, 0.75, 0.645 for identifying community-ac⁃ quired pneumonia and tuberculosis, respectively. CONCLUSION The levels of MMP-9, TIMP-1 and MMP-9/TIMP-1 were different between CAP and PTB, and MMP-9 and MMP-9/TIMP-1 have certain diagnostic value between CAP and PTB.