Bone Metabolism Assessment in Hemodialysis Patients by Using Carboxy-Terminal Cross-Linked Telopeptide of Type I Collagen

Aims: To evaluate the carboxy-terminal telopeptide of type I collagen (CTX I) as a serum bone metabolism marker in hemodialysis patients.

Study Design: Cross-sectional observational.

Place and Duration of Study: Hemodialysis unit of Tanta University Hospital, between October 2018 and March 2020.

Methodology: 80 male patients aged from (18-65y) on regular hemodialysis were included. All patients were subjected to: history taking, full clinical examination, laboratory investigations including: Serum calcium, serum phosphorus, serum albumin, alkaline phosphatase (ALP), Intact parathyroid hormone (iPTH), serum carboxy-terminal cross linking telopeptide (CTX I) and dual energy X ray absorptiometry (DEXA) scan of the lower third of the right fibula to evaluate bone mineral density (BMD) and patient were divided according to bone mineral density T score into two groups "normal and osteopenic groups".

Results: There is significant difference between normal and osteopenic groups according to iPTH (p = 0.001) and ALP (p = 0.001) and CTX I (p = 0.001), but there is non-significant difference between normal and osteopenic groups according to serum calcium (p =0.239), serum phosphorus (p =0.672), serum albumin (p =0.749) and corrected serum calcium (p = 0.314).There was negative significant correlation between CTX I and DEXA scan, and between DEXA scan and iPTH and ALP. There was positive significant correlation between CTX I and iPTH, ALP and serum albumin and there was positive significant correlation between iPTH and ALP. At cutoff 2.0 ng/ml CTX I can significantly diagnose osteopenia in hemodialysis patients with 93% sensitivity, 95% specificity and accuracy of 92%. It had positive predictive value of 95% and negative predictive value of 83%, in multiple regression analysis the increase in iPTH and CTX I was the significant predictor of osteopenia.

Conclusion: This study showed high association between CTX I and other established markers of bone metabolism and BMD by DEXA demonstrating the potential utility of CTX I as marker of bone resorption in renal bone disease.