A HARFORD1, H JIANG2, S PAINE2, VS PANKRATZ1, A GUL2, P ZAGER1,2
1University of New Mexico Health Sciences Center, Albuquerque , United States, 2Dialysis Clinic, Inc., Albuquerque, United States
Aim: Describe the intra-individual variability in serum parathyroid hormone (PTH) concentrations in chronic hemodialysis (HD) patients to assess the suitability of using PTH to drive protocols for dosing calcimimetics and vitamin D.
Background: The use of serum PTH concentrations to adjust calcimimetic and vitamin D dosing does not account for the complex secretory dynamics of PTH, which reflect tonic and pulsatile secretion.
Methods: To assess variability in serum PTH we studied 25,307 prevalent patients treated with thrice weekly HD in clinics operated by Dialysis Clinic Inc., from March 31, 2015 to March 31, 2018. We constructed mixed models to compute intraclass correlation coefficients (ICC) of log-transformed PTH concentrations adjusted for age, sex, race, ethnicity, vintage, diabetes status, serum calcium, phosphorous, and albumin.
Results: At study start patients were in four groups with respect to cinacalcet and vitamin D: (1) cinacalcet and vitamin D (n=3128), (2) cinacalcet alone (n=870), (3) vitamin D alone (n=10,720), and (4) no cinacalcet or vitamin D (n=10,589). During the study period 14,060 patients had ≥ 1 change in cinacalcet or vitamin D treatment combinations (median time to the first change was 130 days). The mean and (standard deviation) of the individual maximal differences ranged from 105 (330) to 821 (699) pg/ml. The adjusted ICCs were higher among patients who did not change 0.68 (95% CI 0.68, 0.69) vs. those who changed medications 0.53 (95% CI 0.52, 0.54). Although there were significant differences in the degree of variability between groups all ICCs were <0.75.
Conclusion: The low ICCs suggest that high intra-individual variability in serum PTH concentrations complicates the use of PTH to drive clinical protocols for dosing calcimimetics and vitamin D.
Antonia Harford is a Professor of Medicine, Division of Nephrology in the Department of Internal Medicine, at the University of New Mexico Health Sciences Center. She is the Medical Director of the University of New Mexico (UNM) Renal Transplant Program. Dr. Harford’s research interests include health outcomes in End Stage Renal Disease patients and transplant access issues.