Hyperparathyroidism in chronic kidney disease: a retrospective cohort study of costs and outcomes.

Hyperparathyroidism may play a role in the excess morbidity and mortality in chronic kidney disease. This study examined utilization and outcomes of patients with hyperparathyroidism and chronic kidney disease. In a US health maintenance organization (HMO), patients with chronic kidney disease were identified from the electronic medical record. Patients included in the study had at least one intact parathyroid hormone (iPTH) measurement ordered by a nephrologist and were at least 20 years of age with no history of renal replacement therapy (RRT, n = 455). Cohorts were determined by index iPTH level and were followed for 1 year. Rates of health care utilization were compared between cohorts using Poisson regression; costs comparisons were made using linear regression; mortality and RRT were evaluated using Cox regression. Increasing levels of iPTH were associated with a significantly elevated risk of mortality and RRT, even after adjustment for potential confounders such as stage of chronic kidney disease. Compared to iPTH of <110 pg/ml, we found a 66% increase combined mortality-RRT risk (HR 1.66, 95% CI 1.41-1.97) for those with iPTH 110-199 pg/ml, and a HR of 4.57 (95% CI 3.86-5.43) for iPTH >or=300 pg/ml. We did not find a convincing association between iPTH level and utilization. While this study provides no evidence that treating patients with higher levels of iPTH will ameliorate poor outcomes, it suggests that iPTH levels beyond the targets suggested by clinical guidelines are associated with increased harm in patients with chronic kidney disease.