Comparison of Serum Calcium, Phosphorus, Alkaline Phosphatase, and Intact Parathyroid Hormone Levels Between Dialysis-Dependent and Non-Dialysis-Dependent Patients With Chronic Kidney Disease: A Cross-Sectional Observational Study.

Background  Chronic kidney disease (CKD) is frequently accompanied by chronic kidney disease-mineral and bone disorder (CKD-MBD), a systemic complication characterised by biochemical abnormalities in serum calcium, phosphorus, alkaline phosphatase (ALP), and intact parathyroid hormone (iPTH), which may contribute to bone disease, vascular calcification, cardiovascular morbidity, and adverse clinical outcomes. Aim  This study aimed to compare serum calcium, phosphorus, ALP, iPTH, and calcium-phosphorus product levels between dialysis-dependent and non-dialysis-dependent patients with CKD and to assess the associations of these biochemical parameters with dialysis duration. Materials and methods  This hospital-based comparative observational study included 120 adults with CKD attending a tertiary care centre in Kanpur, India, comprising 60 dialysis-dependent and 60 non-dialysis-dependent patients aged 18-65 years with CKD stages 3-5. Patients were enrolled consecutively during the eight-month study period following Institutional Ethics Committee approval. Serum calcium, phosphorus, ALP, and iPTH values were obtained as part of routine clinical evaluation and retrieved from the patients' hospital records. In dialysis-dependent patients, blood samples were collected before a scheduled hemodialysis session; in non-dialysis-dependent patients, values were obtained from routine clinical laboratory assessments. The calcium-phosphorus product (Ca × P) was calculated from the recorded calcium and phosphorus values. Statistical analysis was performed using IBM SPSS Statistics, version 26.0 (IBM Corp., Armonk, NY, USA), with p < 0.05 considered statistically significant. Results  Serum calcium was significantly lower, whereas serum phosphorus, ALP, iPTH, and calcium-phosphorus product were significantly higher in dialysis-dependent than in non-dialysis-dependent patients with CKD (all p < 0.001). All dialysis-dependent patients had stage 5 CKD. Among dialysis-dependent patients, dialysis duration showed significant positive correlations with serum phosphorus, ALP, and iPTH and a significant negative correlation with serum calcium. Conclusion  CKD-MBD abnormalities were more pronounced in dialysis-dependent than in non-dialysis-dependent patients with CKD. Longer dialysis duration was associated with lower serum calcium and higher serum phosphorus, ALP, and iPTH levels. These findings support regular surveillance of these biochemical parameters for timely recognition and management of CKD-MBD.