Variation in Oral Calcitriol Response in Patients With Stages 3-4 CKD

Background: Oral calcitriol decreases parathyroid hormone (PTH) concentrations in patients who have chronic kidney disease (CKD); however, treatment response is highly variable. We evaluated whether patient characteristics affect the PTH response to oral calcitriol in nondialysis patients with CKD in a clinic-based setting. Study Design: Cohort study. Setting & Participants: This study included 379 new oral calcitriol users in the Veterans' Affairs Northwest Health Network. All had stages 3-4 CKD, hyperparathyroidism, and a serum PTH measurement before and 1-6 months after initiating oral calcitriol therapy. Predictors: Patient-level characteristics hypothesized to affect calcitriol response: race, body size, concurrent medications, and kidney function. Outcomes: Relative decrease in serum PTH concentration after starting oral calcitriol therapy. Measurements: Data were abstracted from the Veterans' Affairs Northwest Health Network (VISN 20) Data Warehouse, which includes electronic pharmacy and laboratory records. Results: Mean estimated glomerular filtration rate was 30 mL/min/1.73 m(2) and mean initial PTH concentration was 199 pg/mL. Regular- (0.25 mu g/d) and low-dose (<0.25 mu g/d) oral calcitriol were associated with on average 23% and 13% relative decreases in serum PTH concentrations, respectively. After adjustment for calcitriol dosage, initial PTH concentration, and time to follow-up measurement, African American race was associated with a blunted calcitriol response (geometric mean final PTH value, 26% higher; 95% CI, 8%-47%). Serum albumin concentration <3.5 g/dL also was associated with a diminished calcitriol response (geometric mean final PTH, 19% higher; 95% CI, 6%-35%). Although numbers were small, concurrent use of benzodiaz-epines and nonactivated vitamin D supplements was associated with a significantly greater PTH response. Limitations: Clinic-based study is limited by the availability of PTH measurements after starting calcitriol therapy. Study of a predominantly older male population. Conclusions: In patients with stages 3-4 CKD, African American race and low serum albumin level are associated with a diminished PTH response to oral calcitriol. Am J Kidney Dis. 59(5): 645-652. (C) 2012 by the National Kidney Foundation, Inc.