pth levels and not serum phosphorus levels are a predictor of the progression of kidney disease in elderly patients with advanced chronic kidney disease

Background: At present, there is a high incidence of elderly patients with advanced chronic kidney disease (CKD) and it is important to know the long term progression and the factors that influence it. Objectives: To analyse the progression of advanced CKD in elderly patients and the influence of bone-mineral metabolism. Methods: Retrospective study of 125 patients ≥70 years of age with CKD stages 4–5 who started follow-up from January 1, 2007 to December 31, 2008, showing the progression of CKD (measured by the slope of the regression line of the estimated glomerular filtration rate [eGFR] by MDRD-4) over 5 years. Results: Progression in the entire group (median and 25th and 75th percentiles): −1.15 (−2.8/0.17) ml/min/1.73 m2/year, CKD-4: −1.3 (−2.8/0.03) ml/min/1.73 m2/year, CKD-5: −1.03 (−3.0/0.8) ml/min/1.73 m2/year; the slope of the regression line was positive in 35 patients (28%: CKD does not progress) and negative in 90 patients (72%: CKD progresses). Negative correlation (Spearman) (slower progression): PTH, albumin/Cr ratio and daily Na excretion (all baseline measurements). No correlation with eGFR, serum P, urinary P excretion, protein intake and intake of P (all baseline measurements). In the linear regression analysis (dependent variable: slope of progression): albuminuria and PTH (both at baseline measurements) influenced this variable independently. Logistic regression (progresses vs. does not progress): PTH, albuminuria and eGFR (all at baseline measurements) influenced significantly. Conclusions: In our group of elderly patients, impairment of renal function is slow, particularly in CKD-5 patients. Albuminuria and PTH at baseline levels are prognostic factors in the evolution of renal function.