Estimation of glomerular filtration rate determination of proteinuria and albuminuria

Abstract:

The most sensitive method for assessment of the status of renal function is glomerular filtration rate (GFR) which is expressed and measured as clearance. Creatinine is a metabolite that is mostly excreted through glomerular filtration and its clearance has for decades been used in clinical practice as the gold standard substitute for exogenous substances. Today, GFR estimation allows us to avoid unreliable urine collection and refers us to empirical equations to calculate GFR with less errors on the basis of serum creatinine, provided that we use a reliable analytical method. Increased protein/albumin turnover is nephrotoxic and predictive of renal disease progression. Sensitivity and specificity of biochemical methods have changed our points of view so that even urinary albumin elevated within the reference interval indicates an enhanced risk for renal disease. Analytical methods for albuminuria have recently been developed and immediately applied by introduction of immunochemistry in medical biochemistry. The cornerstones of modern nephrology are three analytical approaches: screening semiquantitative method, quantitative method for protein/albumin determination in 24 h urine, and protein/albumin and creatinine concentration ratio in spot urine which may replace the traditional reference method that uses 24 h urine specimen. 

Key words:
albuminuria, proteinuria, creatinine clearance, glomerular filtration rate, empirical formulas