Indicators of Renal Impairment in Laboratory Tests

Serum Creatinine and GFR

• Elevated serum creatinine is a key indicator of reduced renal function, reflecting decreased glomerular filtration 1
• A low estimated glomerular filtration rate (eGFR) calculated from serum creatinine indicates renal impairment - values below 60 ml/min/1.73 m² indicate chronic kidney disease stage 3 1, 4
• Increased (not decreased) GFR is not associated with renal impairment; in fact, decreased GFR is the hallmark of kidney dysfunction 2, 3

Blood Urea Nitrogen (BUN)

• Elevated BUN reflects reduced kidney function and has been shown to correlate with reduced renal blood flow 1

Proteinuria

• Protein in urine (proteinuria) is a significant marker of kidney damage and glomerular filtration barrier derangement 1, 2
• Proteinuria indicates established renal parenchymatous damage and is associated with increased cardiovascular risk 1, 3
• Microalbuminuria (low-grade albuminuria) predicts the development of overt diabetic nephropathy and cardiovascular events 2, 4

Important Clinical Considerations

• Both formulae for estimating GFR (MDRD and Cockcroft-Gault) help detect mild impaired renal function even when serum creatinine values are still in the normal range 1, 5
• Monitoring trends in renal function markers is often more informative than single measurements, particularly when evaluating medication effects 7
• Early detection of renal impairment is critical as it constitutes a potent predictor of future cardiovascular events and mortality 1, 8