Effect of extended hours dialysis on markers of chronic kidney disease-mineral and bone disorder in the ACTIVE Dialysis study

BACKGROUND: Chronic Kidney Disease - Mineral and Bone Disorder (CKD-MBD) is a significant cause of morbidity among haemodialysis patients and is associated with pathological changes in phosphate, calcium and parathyroid hormone (PTH). In the ACTIVE Dialysis study, extended hours dialysis reduced serum phosphate but did not cause important changes in PTH or serum calcium. This secondary analysis aimed to determine if changes in associated therapies may have influenced these findings and to identify differences between patient subgroups. METHODS: The ACTIVE Dialysis study randomised 200 participants to extended hours haemodialysis (≥24 h/week) or conventional haemodialysis (≤18 h/week) for 12 months. Mean differences between treatment arms in serum phosphate, calcium and PTH; and among key subgroups (high vs. low baseline phosphate/PTH, region, time on dialysis, dialysis setting and frequency) were examined using mixed linear regression. RESULTS: Phosphate binder use was reduced with extended hours (− 0.83 tablets per day [95% CI -1.61, − 0.04; p = 0.04]), but no differences in type of phosphate binder, use of vitamin D, dose of cinacalcet or dialysate calcium were observed. In adjusted analysis, extended hours were associated with lower phosphate (− 0.219 mmol/L [− 0.314, − 0.124; P < 0.001]), higher calcium (0.046 mmol/L [0.007, 0.086; P = 0.021]) and no change in PTH (0.025 pmol/L [− 0.107, 0.157; P = 0.713]). The reduction in phosphate with extended hours was greater in those with higher baseline PTH and dialysing at home. CONCLUSION: Extended hours haemodialysis independently reduced serum phosphate levels with minimal change in serum calcium and PTH levels. With a few exceptions, these results were consistent across patient subgroups. TRIAL REGISTRATION: Clinicaltrials.gov NCT00649298. Registered 1 April 2008. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12882-019-1438-3) contains supplementary material, which is available to authorized users.