ObjectiveTo investigate the relationship between platelets changes and outcomes of acute respiratory distress syndrome (ARDS) patients.MethodsA total of 275 ARDS patients treated in Zhongshan Hospital of Fudan University were retrospectively enrolled from 2008 to 2015. Their clinical characteristics, experimental test results and disease outcomes were obtained from the archived medical records. The correlation between the decreasing of platelet within three days and the prognosis of ARDS and in each subgroup were analyzed by statistical methods, including COX analysis and Kaplan-Meier curve.ResultsThere were 233 patients validly selected through eliminating those with exclusion criteria. They were divided into a decreasing group and a non-decreasing group according to their platelet counts in three days. There was significant difference in the ontcome between the two groups with the univariate analysis, the COX analysis and Kaplan-Meier curve (all P<0.05). According to the initial platelet count and change of platelet in 3 days all the patients were categorized into 9 subgroups. The mortality among them was compared and two risk groups were defined, including a persistently low platelet group (the initial platelet count <139×109/L with an increase less than 16×109/L during the first three days after the diagnosis), and a decreased platelet group (the initial platelet count ≥139×109/L and platelet count decreased more than 30×109/L during the first three days after the diagnosis). The other subgroups made up a non-risk group. Merging two risk groups as one risk group and comparing with the non-risk group, there were significant differences in the outcome between two groups with the univariate analysis, the multiplicity COX analysis and Kaplan-Meier curve (all P<0.05), the differences of coagulation function indexes were not significant (allP>0.05). The platelet count of the risk group was also an independent risk factor for ARDS mortality in the surgery subgroup (P=0.003), the non-hypertension subgroup (P=0.018) and the pneumonia subgroup (P<0.001).ConclusionLow platelets and declining platelets are closely associated with poor prognosis in most ARDS patients, which might be applied in clinical prognosis evaluation.