| Sumario: | 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 (CL...) levels. The following equations were also used to determine the estimated GFR that was compared with the reference CL... 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 CL..., whereas overestimation by every SCr-based formula was observed in the whole cohort and in the CL...< 60 mL/min/1.73 m² 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 CL... of <60 mL/min/1.73 m ², where the MDRD equation showed better results than the cystatin C-based equation (33.5% versus 38.9%). No equations fulfilled concordance requirements with CL.... 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.
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