#4554 FRAX® ASSOCIATION, BONE DENSITOMETRY, BIOCHEMICAL PARAMETERS OF BONE MINERAL METABOLISM AND ADVANCED CHRONIC KIDNEY DISEASE
Authors: Gómez Cristina Andrades , Cosano Gema Montilla , Oporto Francisco Roca , Collado Alba Temprado , Blandino Marisa Vidal , Prieto Francisco Javier Toro 
Published: June 2023

Abstract

Background and Aims
Currently, there are calculation tools that predict the risk of fractures (fx), one of which is the Fracture Risk Assessment Tool (FRAX®). Patients with advanced chronic kidney disease (CKD) have a higher risk of fx than the general population and it is an independent factor for fx. However, this tool does not consider the presence or absence of CKD, where alterations in bone mineral metabolism have important clinical consequences and their prevention should be the objective of CKD control. The aim of our study is to evaluate the FRAX® tool in patients with advanced CKD and to analyze possible relationships with parameters of bone mineral metabolism.

Method
Observational, descriptive, retrospective study of a series of cases of patients with advanced chronic kidney disease in our center, where demographic data, FRAX® calculation, personal history of Diabetes Mellitus, etiology of CKD, personal history of fx, measurement of bone mineral densitometry by dual energy X-ray absorptiometry (DXA), estimated glomerular filtration rate (CKD-EPI), levels of serum calcium and phosphorus, vitamin D 1. 25 levels, Parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23), use of phosphorus chelating treatment and vitamin D were collected. Descriptive results of continuous variables are expressed as mean and standard deviation or median and interquartile range (IQR) according to their distribution. For categorical data, frequency and percentage are reported. To analyze the impact of the variables on the event to be studied, a univariate and multivariate Cox regression model was used.

Results
59 patients with advanced CKD with DXA performed within one year of the FRAX® analysis were analyzed. The median age was 66 years (IQR 22). 59.3% were male. 35.6% had a personal history of diabetes mellitus. The most frequent etiology of CKD was unknown etiology (18.6%), followed by vascular (16.9%). History of some type of fx:13.6% (3.6% vertebral). Estimated glomerular filtration rate CKD-EPI: 20.7 ml/min/1,73 m2 (IQR 7.5). 16.9% had osteoporosis of the femoral neck and 22% of the spine. DXA decreased in femoral neck 78% and in spine 59.3%. Low risk of major osteoporotic fracture according to FRAX® of 76.3% and 64.3% (without and with DXA) and elevated risk of major osteoporotic fracture according to FRAX® 5.1% and 8.5% (without and with DXA). Risk of hip fracture 25.4% and 30.5% (without and with DXA). These data are summarized in Figure 1 and Figure 2. In the multivariate analysis there is no relationship between bone mineral metabolism parameters and DXA. The results showed a negative correlation between glomerular filtration rate CKD-EPI and FRAX® hip (HR -1.7; 95% CI 1.46-9.6 p = 0.027) which would suggest an association between loss of renal function and loss of DXA. Patients with diabetes mellitus have a higher risk of fx (HR 3.7; 95% CI 1.46-9.6 p = 0.009).

Conclusion
In patients with advanced CKD, FRAX® index identifies patients at high fracture risk for whom active treatment for osteoporosis should be instituted. In patients with advanced chronic kidney disease, FRAX® underestimates those patients with decreased bone mass and elevated risk of osteoporosis. We did not find any association with biochemical parameters of bone mineral metabolism which could guide us in anticipating the treatment of osteoporosis. The loss of renal function accelerates the loss of bone mass, so we believe that the introduction of this variable is necessary in the equation, especially in this profile of patients.