How Robust are our Methods of Detecting Impaired Glomerular Filtration Rate in the Intensive Care Unit?

Area of Science:

• Nephrology
• Critical Care Medicine
• Clinical Chemistry

Background:

• Serum creatinine lacks sensitivity for early acute kidney injury (AKI) detection.
• Existing formulas for predicting glomerular filtration rate (GFR) and timed creatinine clearance require validation in AKI contexts.

Purpose of the Study:

• To evaluate the sensitivity of formula-based GFR estimation and timed creatinine clearance compared to measured GFR in intensive care unit (ICU) patients.
• To assess the agreement between different GFR estimation methods in patients with apparent normal renal function on ICU admission.

Main Methods:

• Prospective observational study involving 50 adult ICU patients with initially normal renal function.
• Assessed GFR using timed creatinine clearance and various predictive formulas.
• Statistical analysis included Spearman correlation and Bland-Altman plots to compare methods.

Main Results:

• 50% of patients had a one-hour urinary creatinine clearance <80 ml/min/1.73m(2), indicating potential early renal impairment.
• Significant correlations were found between formula methods and measured creatinine clearance.
• Bland-Altman analysis revealed substantial disagreement between predictive equations and measured creatinine clearance, with wide confidence intervals.

Conclusions:

• Formula methods and creatinine clearance offer greater sensitivity than serum creatinine for detecting early AKI.
• Despite correlation, significant discrepancies exist between various GFR estimation methods, limiting their interchangeable use in clinical practice.