Serum Calcium and Phosphorus Levels in Hemodialysis Patients: A Large Population-Based Multicenter Study

Mineral bone disorder is one of the major factors affecting mortality and morbidity in dialysis patients, which is called chronic kidney disease-mineral and bone disorder (CKD-MBD). This study aimed to evaluate the laboratory parameters of mineral bone disorder in hemodialysis patients in Iran and their relationship with malnutrition and inflammation. This multicenter observational study was conducted in 2016 in 58 dialysis centers in Iran. Data of a total number of 7191 chronic hemodialysis patients aged older than 18 years with a dialysis duration of > 3 months were collected. Idiopathic hypercalcemia and history of parathyroidectomy were considered as the exclusion criteria. The serum levels of calcium (Ca), phosphorus (P), and intact parathyroid hormone (iPTH) were measured over a period of three months, and the findings were compared with the K/DOQI (National Kidney Foundation Dialysis Outcomes Quality Initiative) guidelines. Moreover, the serum level of C-reactive protein (CRP) and nutritional status based on geriatric nutritional risk index (GNRI) were assessed. The percentage of the patients who had a serum iPTH level of < 150 pg/mL was 46% while that of patients with iPTH of > 300 pg/mL was 29.3%. Hypercalcemia and hyperphosphatemia were observed in 20.6% and 34.2% of the patients, respectively. Moreover, 51.7%, 61.3%, 24.7%, and 84.7% of the patients, respectively, reached the K/DOQI target range of Ca, P, iPTH, and Ca × P product. The percentages of mild-to-severe malnutrition based on GNRI in patients whose iPTH level was within, below, and above the recommended range of K/DOQI guidelines were 30.7%, 34.1%, and 25.9%, respectively (P < 0.001). Furthermore, the serum level of CRP was significantly higher in low-serum PTH patients than in the other two groups. In total, only could 8.3% of the patients reach the four KDOQI target levels of CKD-MBD. The findings showed a significant percentage of patients had a low serum PTH level, which might be attributed to inflammatory and nutritional factors. Only had a small percentage of patients reached all the K/DOQI targets. Therefore, the effects of inflammatory and nutritional factors should also be considered, particularly in developing countries.