Abstract: Objective  To evaluate of cystatin C (CysC) on the predictive value of contrast induced nephropathy(CIN) by comparing the changes  of creatinine(SCr) and CysC after coronary arteriography (CAG).Methods  Patients who underwent coronary angiography and/or percutaneous coronary intervention were enrolled. Serum  creatinine and CysC were monitored before angiography， 1 day， 2 days， 3 days after angiography. Glomerular filtration rate was estimated by MDRD. The primary end point was the incidence of CIN. Results  A total of 384 patients were enrolled  in this study， and 16 (4.17%) patients developed CIN according to the SCr criteria. Serum CysC was significantly higher at 1 day， 2 days，3 days after angiography (P＜0.05). The level of serum CysC was positively correlated with SCr level (r=0.313，P<0.01)， but negatively correlated with eGFR (r=-0.325，P<0.01). The area under ROC curve at 2 days after angiography was 0.833（95%CI=0.7440.992，P＜0.01）， better than 1 day and 3 days after angiography. The best cutoff point was 1.115 mg/L. The area under ROC curve of varying degrees at 2 days after angiography was 0.812（95%CI=0.8020.822，P＜0.01）  and the best cutoff point was 12.5%. Conclusion   As serum CysC could evaluate the renal function at early period，it could be   a sensitive biomarker to evaluate induced CIN. The accuracy of diagnosis CIN in CysC level 2 days after CAG was higher than that 1 day and 3 days after CAG. Moreover， ≥12.5%  increase can be used as a cutoff point in CIN diagnosis.

Key words: acute kidney injury;contrast , media；cystatin , C