Abstract: SA-PO691
Modeling Decision Making for IV Vitamin D Titration in Patients on Hemodialysis (HD)
Session Information
- Bone and Mineral Metabolism: Clinical - II
October 27, 2018 | Location: Exhibit Hall, San Diego Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Bone and Mineral Metabolism
- 402 Bone and Mineral Metabolism: Clinical
Authors
- Hall, Rasheeda K., Duke University, Durham, North Carolina, United States
- Wilson, Jonathan A., Duke University, Durham, North Carolina, United States
- Platt, Alyssa C., Duke University, Durham, North Carolina, United States
- Ephraim, Patti, Johns Hopkins University, Baltimore, Maryland, United States
- Weiner, Daniel E., Tufts Medical Center, Boston, Massachusetts, United States
- Boulware, L. Ebony, Duke University, Durham, North Carolina, United States
- Pendergast, Jane F., Duke University, Durham, North Carolina, United States
- Scialla, Julia J., Duke University, Durham, North Carolina, United States
Background
Studies in HD often focus exclusively on parathyroid hormone (PTH) as the driver of intravenous (IV) vitamin D titration. We hypothesized that a constellation of mineral metabolism (MM) laboratories (labs), including calcium (Ca), phosphorus (Pi) and PTH, influence titration.
Methods
We retrospectively studied 62,284 decisions in 5442 patients initiating in-center HD between 2006-2008 in Dialysis Clinic, Inc. facilities with non-missing data. We used multinomial transition mixed models to predict increase, decrease or no change in IV vitamin D based on monthly albumin-corrected Ca, Pi, and PTH using piecewise linear functions with knots at 8.0 and 10.2 mg/dl for Ca, 3.5 and 5.5 mg/dl for Pi, and 150 and 300 pg/ml for PTH, 3 sets of lagged monthly lab values, and interactions between current labs to capture a fully integrated lab phenotype. Adding piecewise functions and lab interactions improved fit as reflected in AIC (66,282 vs. 80,084).
Results
Participants contributed a mean ± SD of 9.3 ± 8.5 treatment months. The PTH threshold at which IV vitamin D is more likely to be increased than decreased is the intersection of solid (probability of increase) and dashed (probability of decrease) lines (Figure). This threshold PTH is higher when Ca and Pi were higher, demonstrating that Ca and Pi influence providers’ effective PTH titration goal. Titration or addition of alternative therapies, such as cinacalcet, are not depicted here, but are also impacted by integrated lab phenotypes (data not shown).
Conclusion
Prescribers consider multiple lab dimensions when titrating IV vitamin D. Comparative effectiveness studies and trials in MM may be improved by appropriately capturing complex lab phenotypes that contribute to decision-making.
Funding
- NIDDK Support