Objective:To evaluate the predictive value of angiopoietin-2 (Ang-2) for the prognosis in patients with acute respiratory distress syndrome (ARDS).Methods:A retrospective study was conducted, and ARDS patients admitted to the department of emergency medicine of Tongde Hospital of Zhejiang Province from December 2020 to September 2022 were enrolled. General information including gender, age, causes of ARDS, disease severity scores, plasma Ang-2 levels before treatment and at 24, 48, and 72 hours after treatment, and record the 60-day prognosis were collected. Differences in clinical data between groups were compared. Multivariate Logistic regression analysis was used to identify the independent risk factors affecting the 60-day prognosis of ARDS patients, and the receiver operator characteristic curve (ROC curve) was plotted to assess the predictive value of these risk factors for patient outcomes. Pearson correlation analysis was used to assess the correlation between Ang-2 and pulmonary vascular permeability index (PVPI) and extravascular lung water index (EVLWI).Results:A total of 132 ARDS patients were included, of which 49 patients died within 60 days and 83 patients survived. In the death group, plasma Ang-2 levels showed a gradually increasing trend, all significantly higher than before treatment (μg/L: 12.75±1.81, 12.74±1.48, 13.45±2.21 vs. 5.98±0.57, all P < 0.05), while the trend in the survival group was not significant. At 24, 48, and 72 hours after treatment, plasma Ang-2 levels in the death group were significantly higher than those in the survival group (μg/L: 12.75±1.81 vs. 7.48±1.22, 12.74±1.48 vs. 7.41±1.19, 13.45±1.41 vs. 6.88±1.41, all P < 0.05). After adjusting for confounding variables, increased plasma Ang-2 level was an independent risk factor for prognosis in ARDS patients within 60 days [odds ratio ( OR) = 0.998, 95% confidence interval (95% CI) was 0.997-0.999, P < 0.01]. ROC curve analysis demonstrated that Ang-2 levels had predictive value for prognosis in ARDS patients [area under the ROC curve (AUC) = 0.985, 95% CI was 0.971-1.000, approximate maximum Youden's index 0.867, optimal cut-off value 8.43 μg/L]. Pearson correlation analysis showed that plasma Ang-2 levels were positively correlated with PVPI and EVLWI ( r values were 0.620 and 0.712 respectively, both P < 0.01). Conclusions:Elevated level of Ang-2 is an independent risk factor for increased mortality in patients with ARDS. Higher Ang-2 levels within 72 hours after treatment may indicate poorer prognosis.