Value of creatinine clearance rate estimated based on serum cystatin C in patients with acute kidney injury

Objective To investigate diagnostic value of creatinine clearance rate (CCr) based on serum cystatin C ( SCys C ) in acute kidney injury (AKI),and whether it could predict the need for renal replacement therapy (RRT).Methods The patients enrolled with the length of intensive care unit (ICU) stay over 3 days were collected from August 2010 to May 2011.According to the diagnosis of AKI during the ICU stay,patients were divided into the AKI group (n=21) and non-AKI group (n=30).After patients were admitted,the level of SCysC and creatinine (SCr) were measured so as to count CCr based on SCys C (SCys C-CCr) or on SCr (SCr-CCr) respectively,meanwhile urine volume and acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ ) score were monitored.The value of CCr counted by SCys C and SCr on predict AKI and the correlations between RRT were compared.Results SCr-CCr and SCys C-CCr in AKI group both were significantly lower than non-AKI group all the way through on admission,and 2 days and 1 day before AKI diagnosed and the day AKI diagnosed.The level of SCys C-CCr (ml·min-1· 1.73 m-2) on 2 days prior to AKI diagnosed was significantly lower than the day admitted (70.6 ± 8.4 vs.114.8 ± 15.8,P＜0.01 ),whereas the level of SCr-CCr (ml·min-1· 1.73 m-2) were not significantly changed (76.4 ± 19.3 vs.78.7 ± 22.1,P＞0.05 ).Receptor operative curve ( ROC ) analysis indicated that SCys C-CCr could predict AKI earlier than SCr-CCr,as the area under curve (AUC) of SCys C-CCr and SCr-CCr on 2 days prior to AKI diagnosed were 0.859 and 0.664,respectively,and the sensitivity were 90.5％ and 47.6％,the specificity were 76.2％ and 81.0％.In AKI group 6 patients were treated with RRT,the AKI patients receiving RRT had significantly higher APACHE Ⅱ score on admission (29.6 ± 4.5 vs.17.0 ± 5.6,P＜0.05 ) and less urine volume (ml) within 24 hours (740 ± 465 vs.1780 ± 1230,P＜0.05 ) than patients not received RRT,however,SCys C-CCr has no significant difference between the sub-group (50.4 ± 11.2 vs.53.0 ± 8.4,P＞0.05).SCys C-CCr did not predict the need of RRT on the day to diagnose AKI (AUC =0.65 ).Conclusions The sensitivity of SCys C-CCr were high,but its specificity not.The SCys C-CCr may be helpful for excluding diagnose of AKI in high risk patients.However,it could not predict the need for renal replacement therapy on the day AKI diagnosed. Key words: Cystatin C;  Acute kidney injury;  Creatinine;  Creatinine clearance rate;  Renal replacement therapy