[Laboratory manifestations associated with chronic renal failure: what degree of estimated glomerular filtration can be used for its detection in the elderly?].

OBJECTIVE: A classification of chronic kidney disease (CKD) based on stages of glomerular filtration (GF) has recently been developed. Thus, chronic renal failure (CRF) is based on GF <60 ml/min. Our goal was to study the presence of typical manifestations of CRF in elderly individuals with a GF of <60 ml/min (stage 3-5) and to determine the cut-off value at which GF can be used to detect these manifestations.

MATERIAL AND METHODS: We performed a cross-sectional study in clinically-stable elderly patients attending the geriatrics and nephrology outpatient department. The estimated GF (GFe) was established with the Cockroft-Gault and abbreviated Modification of Diet in Renal Disease Study (MDRD) formulae. Because these patients had a GF of less than 60 ml/min, they were expected to show the manifestations associated with CRF (anaemia, metabolic acidosis, abnormal bone and mineral metabolism). We evaluated the occurrence of these manifestations and the GF cut-off at which they were detected. To do this, the population was divided into two groups: group A: patients with GFe > or = 30 ml/min (stage 3, N=48); and group B: patients with GFe <30 ml/min (stages 4-5, N=8).

RESULTS: Seventy percent of the patients had a GFe (MDRD) <60 ml/min (stage 3-5). Despite reduced GF, these patients did not show the typical manifestations of CRF. Group B showed higher plasmatic levels of creatinine, urea, uric acid, and potassium and required treatment with erythropoietin and calcium salts.

CONCLUSIONS: Many elderly people diagnosed with CKD with the current classification do not show manifestations of CRF. Estimation of the GF in elders should be generalized to correctly adjust medication to renal impairment rather than to classify elders into CKD stage.