Predictive performance of glomerular filtration rate estimation equations based on cystatin C versus serum creatinine values in critically ill patients

Purpose The predictive performance of glomerular filtration rate (GFR) estimation equations based on cystatin C versus serum creatinine (SCr) values in critically ill patients was evaluated. Methods A retrospective observational study was performed in the medical intensive care unit (ICU) of a university hospital from October 2006 through September 2007. All consecutively admitted critically ill patients older than 18 years who stayed in the ICU for more than 48 hours with a urinary bladder catheter in place were included in the study. Data collected included SCr, cystatin C, serum albumin, blood urea nitrogen, and 24-hour urine creatinine clearance ![Formula][1] levels. The following equations were also used to determine the estimated GFR that was compared with the reference ![Formula][2] for all patients in the study: Arnal-Dade using cystatin C, Cockcroft-Gault using actual body weight, Cockcroft-Gault using ideal body weight, Jelliffe, Modification of Diet in Renal Disease (MDRD), and four-variable version MDRD (MDRD-4). Results This study included 241 measurements corresponding to 131 critically ill patients. The cystatin C–based equation underestimated ![Formula][3] , whereas overestimation by every SCr-based formula was observed in the whole cohort and in the ![Formula][4] subgroup; MDRD-4 was the most biased equation in every analysis. There were no significant differences in precision, except for great variability in the subgroup with a ![Formula][5] of . Conclusion A retrospective observational study showed no evidence of superiority of a cystatin C–based equation over SCr-based equations to estimate the GFR in an ICU population. [1]: /embed/mml-math-1.gif [2]: /embed/mml-math-2.gif [3]: /embed/mml-math-3.gif [4]: /embed/mml-math-4.gif [5]: /embed/mml-math-5.gif [6]: /embed/mml-math-6.gif