Assessment of Glomerular Filtration Rate in Clinical Practice

Abstract

Glomerular filtration rate (GFR) is generally considered the best measure of renal function in health and in disease. This is due to the close correlation between filtration capacity and other functions of the kidneys. This review article provides an over-view of the various methods of determining GFR in clinical practice, methods performance and limitations. A Medline literature search was carried out from 1966 to 2006 to assess research and review articles on clinical evaluation of glomerular filtration rate. Additional information was obtained from Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines on evaluation of kidney function. A special consideration was given for articles published in local journals on evaluation of renal function. Only articles published in English language were selected. Inulin clearance is the gold standard against which other markers are compared but it is not practical and inulin is in short supply and difficult to measure. Isotopic methods are also reliable and compare well with inulin clearance; however there are issues of radiation exposure and radionuclide requirements. GFR is often estimated from the measurement of serum creatinine, traditional 24 hours creatinine clearance or formulae equations. The MDRD equation is more accurate in patients with chronic kidney disease while the Cockcroft and Gault equation is useful in individuals with stable renal function. Measurement of plasma cystatin C has been proposed as a new and very sensitive marker of changes in GFR. There is no single test for measuring GFR which is ideally suited for every clinical and research application. Urea and creatinine are the simplest measures of GFR but have several limitations. Creatinine clearance is the best practical measure of GFR but limited by accuracy in urine collection. Plasma cystatin C measurement is a very sensitive marker of changes in GFR and will soon be available for clinical use. The formulae equations provide a quick estimate of the GFR without need for urine collection and are therefore recommended for use in clinical practice. It is believed that widespread use of these formulae equations will lead to substantial improvement in the identification of chronic kidney disease.

Keywords: Renal function, glomerular filtration rate

The Nigerian Medical Practitioner Vol. 52 (4) 2007: pp. 76-81