Vitamin D Status and Treatment in ESKD: Links to Improved CKD-MBD Laboratory Parameters in a Real-World Setting

Introduction: Vitamin D insufficiency is common in patients who receive hemodialysis, yet there is no clear guidance regarding surveillance or treatment. We hypothesized that increasing 25(OH)D₃ levels is associated with lower phosphate, parathyroid hormone (PTH), and alkaline phosphatase (ALP). Methods: Baseline 25(OH)D₃ level was measured in all patients receiving in-center hemodialysis in June 2017. Laboratory parameters were measured every 6 (phosphate, calcium) or 12 weeks (25(OH)D₃, PTH, ALP) until February 2021. In September 2018, a treatment algorithm of 50,000 IU weekly until sufficient followed by 50,000 IU monthly was suggested. Generalized linear mixed regression models including linear spline effects, a log link function, and random effects were used to examine the impact of increasing 25(OH)D₃ levels on calcium, phosphate, ALP, and PTH. Results: Of 697 participants, 15% and 57% had vitamin D deficiency (25(OH)D₃ <25 nmol/L) and insufficiency (between 25 and 74 nmol/L). Incorporating up to 7,272 observations, increasing 25(OH)D₃ was associated with significantly decreasing PTH for 25(OH)D₃ levels between 25 and 75 nmol/L regardless of vitamin D treatment. In an interaction model, the negative slope between 25(OH)D₃ and PTH remained significant beyond 75 nmol/L in the absence of calcitriol. Increasing 25(OH)D₃ was associated with significantly decreasing phosphate for 25(OH)D₃ levels between 25 and 75 nmol/L regardless of vitamin D treatment and below 25 nmol/L in values of untreated patients. Calcium increased across the spectrum of 25(OH)D₃ regardless of vitamin D treatment. Overall, 0.2% of 25(OH)D₃ levels exceeded 250 nmol/L and 2.1% of calcium levels exceeded the normal range. Conclusions: Vitamin D treatment in a real-world setting was safe and associated with lower PTH levels. Whether improved biochemical markers translate to a reduction in clinical endpoints warrants further study.