Abnormal Serum Parathyroid Hormone, Calcium or Phosphate in Patients with Chronic Kidney Disease in Primary Care

Background: In Chronic Kidney Disease (CKD), abnormalities of mineral metabolism can occur early in the disease process. Changes in calcium and phosphate homeostasis and secondary hyperparathyroidism are metabolic complications of CKD that have impact on cardiovascular health and bone turnover. Objectives: To determine the prevalence of mineral metabolism disturbance in CKD in primary care. Methods: In a cross sectional study in nine primary care practices in the Netherlands we evaluated abnormalities of mineral metabolism in CKD patients and identified predictors of these abnormalities. In patients with an eGFR < 60 ml/min/1.73 m2, identified during their evaluation for hypertension or diabetes mellitus, we determined the prevalence of abnormal values of parathyroid hormone (PTH), calcium and phosphate. Predictors of abnormal PTH levels were assessed. Results: A total number of 174 patients in primary care was investigated. Mean eGFR was 50.3 ml/min/1.73 m2. An increase in PTH level above normal occurred in 40% of these patients with early stage of CKD in primary care. Although eGFR predicted abnormal PTH levels, its predictive value was low. Calcium and phosphate abnormalities were infrequent. Conclusion: PTH testing deserves attention in patients with CKD in primary care. Prospective studies should clarify whether PTH lowering affects cardiovascular prognosis of these patients. Awaiting this evidence, we suggest to follow the K-DOQI guideline that advises PTH testing in patients with CKD stage 3 or worse and to treat patients with elevated PTH levels with vitamin D.