2034 CKD-MBD management: results from a national survey on bone turnover biomarkers practice and therapeutic strategies among Italian nephrologists

Abstract Background and Aims Advanced stages of chronic kidney disease (CKD) are constantly characterized by a mineral and bone disorders (MBD) syndrome concerning a complex systemic condition that includes laboratory abnormalities of bone and mineral metabolism involving calcium, phosphorus, parathyroid hormone (PTH), or vitamin D; abnormalities in bone turnover, mineralization, volume, or strength; extra-skeletal calcifications, such as vascular or other soft tissue. CKD-MBD syndrome determines relevant consequences in terms of fragility fractures, cardiovascular events and higher mortality. The nephrologist's awareness of CKD-MBD diagnostic and management tools and therapeutic strategies is key to improving CKD patients’ prognosis and outcomes. Method A new national survey (composed of 17 online questions) was conducted among Italian nephrologists to investigate the reference laboratory availability of bone turnover markers (BTMs), the clinical attitude on secondary hyperparathyroidism (sHPT) management, and the CKD-MBD therapeutic approach in different stages of CKD and dialysis patients. Results 89 Italian nephrologists participated in the survey. The reference laboratories largely fulfill the biomarkers request of ionized calcium (97.7%), phosphorus (100%), PTH (100%), alkaline phosphatase (ALP) (100%), magnesium (100%), 25-OH and 1,25-OH vitamin D levels (92.1%; 53.9%); while most of the hospital laboratories do not regularly support the availability of specific BTMs, both for diagnosis and monitoring the bone resorption and formation (Fig. 1)—such as bone ALP (75.3%), calcifediol (37.1%), calcitriol (40.5%), fibroblast growth factor-23 (FGF-23) (intact 9% and c-terminal 4.5%), vitamin K (33.7%), Klotho (6.75%, soluble 4.5%), osteocalcin (38.2%), matrix gla protein (10.1%), tartrate-resistant acid phosphatase 5b (TRAP-5b) (6.75%), cross-linked collagen type I peptide (CTX) (32.6%) and procollagen type 1 n-terminal propeptide (P1NP) (10.1%). The nephrologist's attitude to start management and treatment of sHPT is revealed to be mainly led by KDOQI (n = 42, 47%) and KDIGO (n = 39, 44%) guidelines considering their PTH cut-off values; in 53.9% of clinicians the measure of PTH levels is then performed every 3 months according to KDOQI guidelines. In relation to the definition of high turnover metabolic bone disease by BTMs, this metabolic pattern is identified in > 50% and 30-40% of patients with CKD 4-5D by 31.5% and 21.4% of nephrologists, respectivel