Abstract

MALHEIRO, Jorge  and  SANTOS, Josefina. Use of equations for glomerular filtration rate estimation in the elderly. Port J Nephrol Hypert [online]. 2014, vol.28, n.1, pp.22-30. ISSN 0872-0169.

Chronic kidney disease (CKD) has been increasingly diagnosed in the elderly, though its clinical significance is still matter of debate. Serum creatinine and cystatin C are the most used endogenous renal function markers. Several equations, usually adjusted for demographical variables, have been derived from them, in order to estimate glomerular filtration rate (eGFR). Serum creatinine levels are influenced by muscle mass so, in patients frequently sarcopenic as the elderly, tends to overestimate renal function. Differently, serum cystatin C seems to improve kidney function estimation in the elderly, although the best performance results have been obtained with equations that include both markers. Creatinine is more widely used than cystatin C, with MDRD and EPI being the most common creatininebased equations. The EPI equation has been shown to improve significantly GFR estimation in subjects with no or mild kidney dysfunction, without jeopardizing eGFR performance in subjects with advanced CKD. Moreover, epidemiological studies have shown that EPI equation may allow a more clinically relevant identification of chronic kidney disease patients. Nevertheless, in the elderly population, one should not overemphasize the issue of GFR accurate estimation, but rather appreciate the probability of kidney dysfunction progression, taking into account the competitive risk between end-stage renal disease and death. Several studies have demonstrated that cystatin C-based (with or without creatinine) equations have considerable better prediction ability than creatinine-only based equations, particularly for death and cardiovascular events. Considering end-stage renal disease, results are more conflicting, although a recent meta-analysis has shown that in the elderly population cystatin C-based equations presented the best predictive behaviour. Thus, we stress the need for an individualized use of glomerular filtration rate equations in the elderly, in whom they should be regarded less as accurate estimators, but more as predictors of clinical outcomes, allowing for their use to be more judicious and clinically relevant.

Keywords : Clinical outcomes; creatinine; cystatin C; renal function.

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