The Study Of Cystatin C In The Early Diagnosis Of Contrast-Induced Acute Kidney Injury

Background and Objective: The diagnosis of contrast-induced acutekidney injury(CIAKI), is mostly according to it’s definition at present, which isbased on the incresement of serum creatinine (sCr) value over0.5mg/dL or therate increase over25%. However, many factors influence sCr, and sCr can notreflect the acute injury of kidney function.Thus, early diagnosis ofcontrast-induced acute kidney injury is becoming important but deficient.Compared with sCr, cystatin C is more sensitive to rapidly detect acutechanges in renal function. This study is undertaken to compare the changes ofcystatin C and sCr before and after expose of contrast media, and assesswhether changes in CyC can be a reliable index for an early diagnosis ofCI-AKI,and provide scientific basis for prevention,early diagnosis and therapyfor contrast-induced acute kidney injury.Methods: This study prospectively analyzes patients undergoing coronaryangiography(CAG) or percutaneous coronary intervention(PCI) in our hospitalbetween June And October in2011. Based on the inclusion and exclusioncriteria,85patients underwengoing intervention for diagnosis and treatment ofcoronary artery disease were enrolled,42males,43females, aged between37to79years old (57.6±9.4years),48patients underwent the coronaryangiography (CAG), while37cases were treated with stent implantation.Before the operation, basic information of the cases were well recorded, such asgender, age, height, weight, blood pressure (including systolic BP, diastolic BP,mean BP), complication with hypertension or diabetes, application ofACEI/ARB. Besides, tests including renal function, and heartfunction(ejection fraction) etc. All patients were treated with conventionalhydration(0.9%NaCl solution intrav-enous injection at1ml/Kg/h12hours before and after the procedure) and water administration (500ml) before andafter the procedure. The dose of CM and procedures were recorded after theoperation, and the renal function was reexamined the minute after theprocedure and on the1stand the3rdday after expose of CM. If ΔScr≥0.5mg/dl,renal function would retested on the7thday. According to the sCr level, thisstudy adopted the simplified MDRD formula to calculate glomerular filtrationrate (GFR), and CIAKI was diagnosed according to the diagnostic criteria ofguidline from the European Society of Urogenital Radiology (ESUR). In thisresearch, all data were analyzed by statistical software SPSS17.0. Continuousvariables were given as mean±1SD, the student t test is used in determiningdifferences between mean values between groups. Categorical variables werereported as percentages and were anlyzed by either Chi-square or Fisher’s exacttest, as appropriate. The ROC analysis is adopted to determine the CyCincrement cutoff point for CIAKI. P<0.05was considered statisticallysignificant.Results: The preoperative cystatin C concentration is about1.09±0.33mg/L. There is no statistical significance(P=0.186) in the cystatin Cconcentration the moment after the operation（1.10±0.31mg/L）. Compared withthe preoperative baseline values, cystatin C concentration24h after theoperation increased significantly(1.14±0.26mg/L，28patients, P<0.05), whileScr had no significant change(P>0.05);72h after the operation, the cystatin Cconcentration return to the baseline value.There is no statistical significancein serum creatinine concentration amongthe preoprative value，the value of the moment after the procedure and24hoursafter the procedure (P>0.05). The creatinine value increase significantly72hafter the operation（P=0.04). According to the diagnostic criteria from theESUR, SCr increase（Scr)≥0.5mg/dl(44.2μmol/l) within24hours occurred in5patients，and9patients within72h. Renal function of the14cases restored well on the7thday, no significant adverse reactions occurred.There is no linear correlation between the24-hour changes of cystatin Cand the ages of patients（F=0.221，P＞0.05）. However, it has positivecorrelation with the dose of contrast media(r=0.037，P＜0.05).Receiver operating characteristic analysis was performed to establish theincrement cutoff value of cystatin C at24hours after the operation forpredicting CIAKI. From the ROC analysis, we found that a cystatin Cincrement≥10%at24hours had a100%sensitivty and a80.3%specificity forpredicting a sCr increase≥0.3mg/dl，and this is the cutoff increment value.Conclusions: Compared with the preoperative baseline values, there is nostatistical significance(P>0.05) in the cystatin C concentration the moment afterthe operation. cystatin C concentration at24h after the operation increasedsignificantly and returned to the baseline72h after the operation. Afterexposure to contrast media, cystatin C increased earlier than the increasementof creatinin, and cystatin C concentration at24hours after the operation is areliable marker for an early detection for CIAKI. The cystatin C increment≥10%at24hours is the cutoff increment value for predicting CIAKI.