Introduction: Abnormal phosphorus homeostasis develops early in chronic kidney disease (CKD). It is unclear if its correction results in improved clinical outcomes in non-dialysis dependent CKD.
Methods: We conducted a randomized controlled, parallel design clinical trial in 120 patients with estimated glomerular filtration rate 15 to 59 ml/min per 1.73 m2 and abnormal phosphorus homeostasis (serum phosphorus >4.6 mg/dl, parathyroid hormone [PTH] >70 pg/ml or tubular reabsorption of phosphorus [TRP] <80%). Patients were randomized to open-label lanthanum carbonate versus calcium acetate versus dietary intervention over 1 year. The co-primary outcomes were month 12 (vs. baseline) biochemical (serum phosphorus, TRP, PTH, calcium, bone-specific alkaline phosphatase [bALP], and fibroblast growth factor 23 [FGF23]) and vascular parameters (coronary artery calcium score, pulse wave velocity, and endothelial dysfunction) in all patients. Secondary outcomes were between-treatment differences in change for each parameter between month 12 and baseline. All analyses were intention to treat.
Results: Baseline characteristics were similar in the 3 groups. A total of 107 patients (89%) completed 12 months of follow-up. Differences were not significant at month 12 (vs. baseline) for any of the outcomes except bALP (median [25th, 75th] percentile at month 12 versus baseline: 13.8 [10.6, 17.6] vs. 15.8 [12.1, 21.1], P < .001) and FGF23 (132 [99, 216] vs. 133 [86, 189], P = .002). Changes for all outcomes were similar in the 3 arms except for PTH, which was suppressed more effectively by calcium acetate (P < .001).
Conclusion: A 1-year intervention to limit phosphorus absorption using dietary restriction or 2 different phosphorus binders resulted in decreased bALP suggesting improved bone turnover, but no other significant changes in biochemical or vascular parameters in patients with CKD stage 3/4. (ClinicalTrials.gov: NCT01357317).
Keywords: FGF23; bone-specific alkaline phosphatase; clinical trial; coronary calcium; parathyroid hormone; pulse wave velocity; serum phosphorus.