Estimates of glomerular filtration rate based on creatinine and cystatin c equations in critically ill patients

Introduction and Aim: Accurate assessment of renal function in the critically ill is a complex task. Estimated glomerular filtration rate (eGFR) is the best indicator to help physicians estimate kidney function and determine different stages of kidney disease. eGFR can be calculated using serum Creatinine (SCr), or serum Cystatin C (SCysC), age, body size, race and gender using different equations. We evaluated eGFR based on SCr and SCysC equations in critically ill patients to find an accurate, precise, and less biased equation for GFR estimation. Methods: This is a single cantered, cross-sectional observational study in critically ill patients older than 18 years staying for over 24-hours in intensive care units. Urinary Creatinine, SCr, and SCysC were measured at 8, 24, and 72-hour intervals. Acute kidney injury (AKI) was defined at admission using the Creatinine definition of the Kidney Disease Improving Global Outcome (KDIGO) guideline. After estimating GFR from Creatinine (eGFRCr), Cystatin C (eGFRCysC), and combining Creatinine and Cystatin C (eGFRCr-CysC), results were compared with measured Creatinine clearance (CrCL). CrCL was defined based on urinary Creatinine, SCr, and urinary volume in a 24-hour period. Results: Forty-three patients were recruited, of which 6 died and 37 alive. eGFRCr-24hrs had the highest correlation to measured CrCL-24hrs, with correlation coefficient of 0.81 (p0.05 for in- hospital-mortality prediction, addressing none of the equations led to death prediction. Conclusions: eGFRCr-24hrs had the highest correlation to measured CrCL-24hrs, with correlation coefficient of 0.81 (p