The Diagnostic Value Of Combining Serum Cystatin C With Creatinine For Contrast-induced Acute Kidney Injury And Its Clinical Implications:A Prospective Cohort Study

Background:Contrast-induced acute kidney injury（CI-AKI）,the third leading cause of hospital-acquired acute kidney injury（AKI）,was traditionally defined as an increase in serum creatinine（SCr）after contrast media exposure within 48-72 hours.This study was a prospective cohort study,aimed to find the diagnostic value of CysC alone or combined with SCr for CI-AKI and their clinical implications.Method:1071 patients undergoing coronary angiography（CAG）or percutaneous coronary intervention（PCI）from July 1,2013 to August 31,2014 were prospectively included.Patients requiring dialysis were excluded.CysC and SCr were assessed at baseline and 24-48 hours after contrast media exposure.CI-AKI_traditional was defined as a SCr increase≥0.3mg/dl or 50%from baseline.Major adverse events（MAEs,including death,myocardial infarction,stoke,revascularization and dialysis）at 1 year were assessed.Results:CI-AKI_traditional developed in 25 patients（2.3%）.The incidence of CI-AKI_traditional rose significantly to 20.0%and 80.0%in patients of chronic kidney disease（CKD）stage 3 and stage 4-5.1-year follow-up was available in 1063 patients（99.2%）and MAEs occurred in 61 patients（5.7%）.By receiver operating characteristic（ROC）curve analysis,a CysC increase≥15%was the optimal increment cut-off value for CI-AKI detection with a 80%sensitivity and a 83%specificity（Positive predictive value:9.6%;negative predictive value:99.4%）and occurred in 187 patients（17.4%）.Patients with a CysC increase≥15%had a higher Mehran score（5.2±3.9 vs 4.4±3.4,P=0.004）and incidence of MAEs（12.4%vs 4.3%,P<0.001）.By multivariate logistic regression analysis,a CysC increase≥15%was a significant predictor of MAEs at 1 year（adjusted odds ratio[OR]=3.04;95%confidence interval[CI],1.75 to 5.29;P<0.001）.Using the composite of CysC（increase≥15%as positive,+）and SCr（increase≥0.3mg/dl or 50%as positive,+）as CI-AKI_new,both CI-AKI low-risk group（CysC+/SCr-or CysC-/SCr+）and high-risk group（CysC+/SCr+）had higher Mehran risk score（4.3±3.4 vs 4.8±3.6 vs9.8±4.4,P<0.001）and incidence of MAEs（4.4%vs 9.8%vs 33.3%,P<0.001）,compared with non CI-AKI group.CI-AKI groups were significantly associated with MAEs at 1 year（Low-risk group:adjusted OR=2.38,95%CI:1.30 to 4.34,P=0.005;high-risk group:adjusted OR=16.56,95%CI:4.49 to 61.12,P<0.001）.Conclusions:A CysC increase≥15%at 24-48 hours after contrast media exposure might have a better sensitivity and negative predictive value in the diagnosis of CI-AKI.The combination of CysC and SCr would be helpful for the risk stratification of MAEs.