Renal function, calcium regulation, and time to hospitalization of patients with chronic kidney disease

BACKGROUND: Chronic kidney disease is associated with disruption of the endocrine system that distorts the balance between calcitriol, calcium, phosphate and parathyroid hormone in the calcium regulation system. This can lead to calcification of the arterial tree and increased risk of cardiovascular disease and death. In this study we develop a health metric, based on biomarkers involved in the calcium regulation system, for use in identifying patients at high risk for future high-cost complications. METHODS: This study is a retrospective observational study involving a secondary analysis of data from the kidney disease registry of a regional managed care organization. Chronic kidney disease patients in the registry from November 2007 through November 2011 with a complete set of observations of estimated glomerular filtration rate, calcitriol, albumin, free calcium, phosphate, and parathyroid hormone were included in the study (n = 284). Weibull regression model was used to identify the most significant lab tests in predicting “waiting time to hospitalization”. A multivariate linear path model was then constructed to investigate direct and indirect effects of the biomarkers on this outcome. RESULTS: The results showed negative significant direct effects of phosphate and parathyroid hormone on “waiting time to hospitalization”. Base on this result, the risk of hospitalization increases 16.8% for each 0.55 mg/dl increase in phosphate level and 13.5% for each 0.467 increase in the natural logarithm of parathyroid hormone. Positive indirect effects of calcitriol surrogate (calcidiol), free calcium, albumin and estimated glomerular filtration rate were observed but were relatively small in magnitude. CONCLUSION: Variables involved in the calcium regulation system should be included in future efforts to develop a quality of care index for Chronic Kidney disease patients.