Our study had several limitations. First,it was a retrospective study in nature,and residual confounding effects existed.Second,we did not record the status of medication,which may affect the levels of Cys-C. 32 Third,the relationship between Cys-C and other parameters,such as troponin and urinary protein, were not comprehensively analyzed in our study. Despite these limitations,our study provided important data on the relationship between Cys-C and the severity of CAD in patients with normal kidney function.