The Performance of Equations That Estimate Glomerular Filtration Rate against Measured Urinary Creatinine Clearance in Critically Ill Patients

摘要

The performance of glomerular filtration rate- (GFR-) estimating equations was studied against creatinine clearance measured by 24-hour urine collection (CrCl 24h-urine ) in critically ill patients. Methods . In this substudy of the PermiT trial ( https://clinicaltrials.gov/ct2/show/ISRCTN68144998 ), patients from King Abdulaziz Medical City-Riyadh who had CrCl 24h-urine were included. We estimated GFR using Cockroft–Gault (CG), modification of diet in renal disease study (MDRD), chronic kidney disease epidemiology collaboration (CKD-EPI), and Jelliffe equations. For the CG equation, we entered the actual weight in one calculation (CG actual-wt ), and if BMI ≥30?kg/m 2 , we entered the ideal body weight (CG ideal-wt ) and the adjusted body weight (CG adjusted-wt ) in two calculations. We calculated the MDRD equation based on 4 (MDRD-4) and 6 variables (MDRD-6). The performance of these equations was assessed by different ways including Spearman correlation, bias (difference between estimated GFR and CrCl 24h-urine ), precision (standard deviation of bias), and Bland–Altman plot analysis. Results . The cohort consisted of 237 patients (age 45?±?20 years, males 75%, mechanically ventilated 99% with serum creatinine 101?±?94? μ mol/L and CrCl 24h-urine 108?±?69?ml/min/1.73?m 2 ). The correlations between the different equations and CrCl 24h-urine were modest ( r : 0.62 to 0.79; ). Bias was statistically significant for CG actual-wt (21?ml/min), CG adjusted-wt (12?ml/min), and MDRD-6 (-10?ml/min) equations. Precision ranged from 46 to 54?ml/min. The sensitivity of equations to correctly classify CrCl 24h-urine 30–59.9?ml/min/1.73?m 2 was 17.2% for CG actual-wt , 30.0% for CG ideal-wt , 31.0% for CG adjusted-wt , 31.0% for MDRD-4, 39.1% for MDRD-6, 13.8% for CKD-EPI, and 34.5% for Jelliffe equation. Conclusions . Commonly used GFR-estimating equations had limited ability to properly estimate CrCl 24h-urine and to correctly classify GFR into clinically relevant ranges that usually determine dosing of medications.