Plasma Parathyroid Hormone Level and Prevalent Cardiovascular Disease in CKD Stages 3 and 4: An Analysis From the Kidney Early Evaluation Program (KEEP)

Background: Cardiovascular disease (CVD) is the most common cause of death in patients with chronic kidney disease (CKD). Secondary hyperparathyroidism is common in patients with CKD, and its relationship to CVD is not well defined. This analysis aims to assess whether serum intact parathyroid hormone (PTH) level is an independent risk factor for CVD in patients with CKD stages 3 and 4. Methods: In this cross-sectional study, medical history surveys, including CVD events, were collected from 4,472 patients with stages 3 and 4 CKD identified by the National Kidney Foundation Kidney Early Evaluation Program (KEEP), which included blood pressure measurement and laboratory testing. Age, hemoglobin level, estimated glomerular filtration rate, serum phosphorus level, and serum calcium level were evaluated as continuous variables, and plasma PTH levels, by tertile: less than 35, 35 to 70, and greater than 70 pg/mL. Multivariate logistic regression was used to estimate odds ratios (ORs) of CVD predictor variables. Results: Mean age was 68.3 +/- 11.8 years. Of the study population, 68% were women, 69% were white, 6% were current smokers, 45% were obese, 46% had diabetes, and 83% had hypertension. A history of CVD was present for 1,972 (44.1%), and plasma PTH level greater than 70 pg/mL, for 2,239 (50.1%). Multivariate logistic regression showed ORs for CVD events increasing with age (OR, 1.03; P < 0.001), male sex (OR, 1.51; P < 0.001), diabetes (OR, 1.73; P < 0.001), hypertension (OR, 1.43; P < 0.001), and intact PTH level greater than 70 pg/mL (OR, 1.51; P < 0.001; reference, <35 pg/mL). Conclusions: PTH level greater than 70 pg/mL is independently associated with CVD events in patients with CKD stages 3 and 4. No association was observed between serum phosphorus or calcium level and CVD events. These findings provide support for intact PTH testing, along with testing for other indicators of CKD mineral and bone disorders, at earlier CKD stages.