Background: Our aims were to determine the rate of progression of chronic kidney disease (CKD) and to identify predictors, with particular emphasis on bone and mineral metabolism.
Methods: Retrospective and observational study including 300 patients with advanced CKD (61.2% males, 33.1% diabetics; age 65.6±14 years). Mean follow-up time was 19.4±10.1 months. Baseline estimated glomerular filtration rate (eGFR) (MDRD-4) was 22.5±7.18 mL/min. To calculate the rate of decline in eGFR, we used the slope of the regression line between all determinations of eGFR and follow-up time. We calculated the mean values for proteinuria and serum phosphate, calcium, uric acid, and PTH, as well as 24-hour urinary excretion of urea nitrogen over time for each patient. Follow-up was at least 6 months and included at least 4 measurements of eGFR.
Results: The mean rate of decline eGFR (-1.64 mL/min/1.73 m²/year) was inversely correlated with serum phosphate levels (4.3±2.1 mg/dL, P<.001), PTH (256.3±193.7 ng/L, p<.001) and proteinuria (0.84±1.31 g/day, P=.004) and directly correlated with mean serum calcium (P<.001) and the presence of hypertension (P<.02). However, only serum phosphate, serum PTH, and proteinuria persisted as predictors in the multivariate analysis. Stable-GFR patients (positive slope) were older (P=.041) and had lower serum phosphate and PTH levels (P<.01 and P<.01 respectively) and lower proteinuria (P<.01).
Conclusions: The rate of decrease in eGFR was correlated with serum phosphate and PTH levels and proteinuria. All of these factors can be modified with an adequate treatment.