Supplementary Material for: Changes in Markers of Mineral and Bone Disorders and Mortality in Incident Hemodialysis Patients

Background: Abnormalities in mineral and bone disorder (MBD) markers are common in patients with chronic kidney disease. However, previous studies have not accounted for their changes over time, and it is unclear whether these changes are associated with survival. Methods: We examined the association of change in MBD markers (serum phosphorus (Phos), albumin-corrected calcium (Ca_Alb), intact parathyroid hormone (iPTH) and alkaline phosphatase (ALP)) during the first 6 months of hemodialysis (HD) with all-cause mortality across baseline MBD strata using survival models adjusted for clinical characteristics and laboratory measurements in 102,754 incident HD patients treated in a large dialysis organization between 2007 and 2011. Results: Across all MBD markers (Phos, Ca_Alb, iPTH and ALP), among patients whose baseline MBD levels were higher than the reference range, increase in MBD levels was associated with higher mortality (reference group: MBD level within reference range at baseline and no change at 6 months follow-up). Conversely, decrease in Phos and iPTH, among baseline Phos and iPTH levels lower than the reference range, respectively, were associated with higher mortality. An increase in ALP was associated with higher mortality across baseline strata of ALP ≥80 U/l. However, patients with baseline ALP <80 U/l trended towards a lower risk of mortality irrespective of the direction of change at 6 months follow-up. Conclusions: There is a differential association between changes in MBD markers with mortality across varying baseline levels in HD patients. Further study is needed to determine if consideration of both baseline and longitudinal changes in the management of MBD derangements improves outcomes in this population.