Objective To investigate the relationship between the expression level of platelet membrane glycoprotein?3(GPⅢa,CD61)and the severity of disease in patients with hemorrhagic fever with renal syndrome(HFRS).Methods One hundred and four patients with HFRS and 30 healthy individuals were recruited.The percentage of CD61 positive platelets and the mean fluores- cence intensities(MFI)of platelet membrane glycoprotein?3 were determined by flow cytometry (FCM).The 104 patients studied were divided into three groups based on their expression levels of platelet membrane glycoprotein?3 at oligurie phase.Clinical data and laboratory parameters in different groups were compared and analyzed.Results The expression levels of CD61 in patients with HFRS were significantly higher than those in control group,although no significant difference in the percentage of CD61 positive platelets between patients with HFRS and controls was detected.The MFI of CD61 expression in patients with HFRS at fever phase,oliguric phase and polyuric phase was 19.75?2.57,17.46?1.48 and 15.55?0.60,respectively,which was significantly higher than that in control group(3 20?0.12).The expression level of CD61 in patients with HFRS at oliguric phase was negatively correlated with platelet count and serum albumin(r=-0.637 and-0.695,respec- tively)and positively correlated with white blood cell count,blood urea nitrogen,serum creatinine and alanine aminotransferase(r=0.945,0.904,0.956 and 0.891,respectively).When the patients were compared according to the expression levels of CD61,it was indicated that the higher the expression level of CD61,the higher the incidence of uremia,hypoalbuminemia,abnormal liver func- tion and leukocytosis.Conclusions The expression levels of platelet membrane glycoprotein?3 in patients with HFRS are different in different clinical phases and are significantly correlated with the severity of the disease in the patients.It suggests that the expression levels of platelet?3 integrin are dramatically increased in patients with HFRS,which may be an indicator for the severity of disease and be helpful for monitoring the state of the patients' diseases and evaluating the severity of the disease.