EVALUATION OF GLOMERULAR FILTRATION RATE IN END-STAGE RENAL DISEAS PATIENTS: OLD AND NEW PREDICTION FORMULAS

摘要

An accurate evaluation of glomerular filtration rate (GFR) is mandatory in patients at the end-stage of chronic kidney disease (CKD stages 4 & 5), to assess the residual renal function, which is an important indicator for initiation of maintenance dialysis. Furthermore, the dosage of many drugs, cleared mainly by the kidneys, must be tapered according to residual renal function, to avoid excessive administration of drugs, which may induce systemic and/or renal toxicity.The gold standards for the measurement of GFR are inulin clearance or radioisotopic methods, which are not feasible to routine use. Therefore, in clinical practice, renal function is commonly evaluated by measuring serum creatinine (SCr) or 24-hour creatinine clearance (CCr). Since creatinine is produced by muscle cells, its daily production is strictly related to the amount of body muscle mass. Thus, SCr is influenced not only by the impairment of GFR, but also by the amount of body muscle mass of individual patients. The measurement of 24h-CCr is not influenced by body composition of the patients. Unfortunately, CCr is neither precise, since it overestimates GFR, neither accurate, due to the high variability of its measurement. Indeed, the major pitfall of CCr is the high variability in the measurement of 24h urinary creatinine excretion (1,2). To overcome this problem different formulas have been proposed to predict GFR from SCr and some anthropometric data (3-6). The accuracy of these formulas is still debated. Recently, we proposed a new method which predicts CCr and GFR from the value of SCr combined with the value of body cell mass (BCM) measured by means of electrical bioimpedance (BIA) (bcmGFR) (7-9). BIA is a simple and validated method to evaluate body composition even in end-stage renal patients (10-12). BCM is the body compartment which is related to muscle mass, where creatinine is produced. Our previous data demonstrate that, in renal patients with different degree of renal function and body mass index, GFR can be predicted from SCr and BCM, more accurately than from 24h CCr and CG CCr (9)Aim of this study was to compare the adequacy of different method used in clinical practice to evaluate GFR in end-stage renal disease (ESRD) patients.