The search for a new marker of renal function in older patients with chronic kidney disease stages 3-4: usefulness of cystatin C-based equations.

BACKGROUND/AIM: Cystatin C (Cys C) is an endogenous marker of glomerular filtration rate (GFR) unaffected by body composition. The aim of the present study was to assess the utility of Cys C-based GFR prediction equations (Hoek, Larsson and Stevens) and creatinine (modification of diet in renal disease-isotope dilution mass spectrometry--MDRD-IDMS, and Cockcroft-Gault--CG) compared with 51Cr-EDTA. METHODS: This study was carried out in 40 Caucasian older patients with advanced age (> or = 60) and chronic kidney disease stages 3-4. To assess the utility of prediction equations in relation to body composition, we measured lean mass (LM) with densitometry (DXA). Pearson's, Bland-Altman and Lin's coefficient (Rc) were used to study accuracy and precision. RESULTS: 51Cr-EDTA was 36.9 +/- 9.2 ml/min/1.73 m2 (22-60). Cys C levels were 2.2 +/- 0.8 mg/l (r = 0.085; p = 0.662 LM) and creatinine 2.8 +/- 1.1 mg/dl (r = 0.427; p = 0.021 LM). The most accurate equations were the Hoek, Larsson and Stevens formulae, with a bias of -0.2 (Rc 0.48), -2.9 (Rc 0.44) and 2.6 ml/min/1.73 m2 (Rc 0.58). The biases obtained with MDRD-IDMS and CG were -14.6 (Rc 0.35) and -12.5 (Rc 0.40). All correlations among biases obtained with creatinine-based formulae and LM were negative and statistically significant (p < 0.05). CONCLUSIONS: The results show superiority of Cys C-based GFR formulae over the MDRD-IDMS and CG equations. This significant underestimation obtained with conventional prediction equations was directly related to the influence of LM.

[Evaluation of candidates for living donor kidney transplantation]. / Valoración de los candidatos a trasplante renal de donante vivo.

Living donor kidney transplantation has become the option of preference for the treatment of endstage renal disease, whenever its performance is possible. The advantages of patient and graft survival should be balanced with risks associated with donation. Therefore, the evaluation of candidates for living donor kidney transplantation is mainly the comprehensive evaluation of these risks: medical, psychological, social and economic. Evaluating risks implies we are treating a controversial process, the medical progress, which is modifiable with time, even in the family and/or social environment of the donor-receptor couple. Short and long-term safety of living donor nephrectomy is directly engaged to the existence of a healthy donor. This he is the main objective of standard evaluation of candidates. Currently, with a growing demand of this option, minor abnormalities or risk factors detected during evaluation do not always become a formal contraindication, but we should try to establish a most objective threshold for the acceptance of donors in all evaluated spheres, for surgical risks and others directly related or not with renal mass reduction, and even for those engaged to the existence of a genetic link between donor and receptor, which might determine the presence of any future primary renal disease. As for other donation types, the process of evaluation should also ensure minimal risks for the receptor, with the same safety criteria applied to cadaver donors. We can conclude that careful evaluation of candidates for living kidney donation is the best guarantee for their safety and transplant success, and, in our opinion, it is the best instrument to offer an adequate informed consent.