CKD-MBD biomarkers and CKD progression: an analysis by the joint model

ABSTRACT Background Biomarkers of chronic kidney disease–mineral and bone disorder (CKD-MBD) have been implicated in CKD progression in follow-up studies focusing on single measurements of individual biomarkers made at baseline only. The simultaneous relationship between the time trend of these biomarkers over the course of CKD and renal outcomes has never been tested. Methods We applied the joint model (JM) to investigate the longitudinal relationship between repeated measurements of CKD-MBD biomarkers and a combined renal endpoint (estimated glomerular filtration rate reduction >30%, dialysis or transplantation) in 729 stage 2–5 CKD patients over a 36-month follow-up. Results In the survival submodel of the JM, the longitudinal series of parathyroid hormone (PTH) values was directly and independently related to the risk of renal events [hazard ratio (HR) (1 ln increase in parathyroid hormone (PTH) 2.0 (range 1.5–2.8), P < .001)] and this was also true for repeated measurements of serum phosphate [HR (1 mg/dl) 1.3924 (range 1.1459–1.6918), P = .001], serum calcium [HR (1 mg/dl) 0.7487 (range 0.5843–0.9593), P = .022], baseline fibroblast growth factor 23 [HR (1 pg/ml) 1.001 (range 1.00–1.002), P = .045] and 1,25-dihydroxyvitamin D [HR (1 pg/ml) 0.9796 (range 0.9652–0.9942), P = .006]. Conclusion Repeated measurements of serum PTH, calcium and phosphate as well as baseline FGF23 and 1,25-dihydroxyvitamin D are independently related with the progression to kidney failure in a cohort of stage 2–5 CKD patients. This longitudinal study generates the hypothesis that interventions at multiple levels on MBD biomarkers can mitigate renal function loss in this population.