P1675BONE DENSITOMETRY IN RENAL TRANSPLANTED PATIENTS
Authors: Ferreira Ana Carina , Mendes Marco , Silva Cecília , Cotovio Patrícia , Aires Inês , Navarro David , Correia Caeiro Pereira Fernando , Salvador Rute , Correia Bruna , Cabral Guadalupe , Nolasco Fernando , Ferreira Manuel Anibal A 
Published: June 2020

Abstract

Background and Aims
Renal transplant and associated immunosuppression can influence bone volume. Presently, the data is conflicting with older studies showing bone loss after transplant, while recent ones didn’t conclude the same. The aim of this study was to analyse the relations between bone-related molecules [phosphorus (Pi), Calcium (Ca), Magnesium (Mg), parathyroid hormone (PTH), bone alkaline phosphatase (bAP), calcitonin, vitamin D (vitD), alpha-klotho, fibroblast grow factor (FGF) 23, sclerostin] and bone densitometry findings in renal transplanted patients.

Method
We performed a prospective cohort study of a consecutive sample of de novo single renal transplanted patients in our unit. At inclusion, demographic, clinical and transplant-related data were collected, X-ray of the pelvis and hands (Adragão score) and echocardiographic findings were recorded. All patients were submitted to a laboratorial evaluation and a bone biopsy at baseline (time 0). Patients were followed for 12 months, after which performed laboratorial evaluation, 2nd bone biopsy, echocardiogram, X-ray of pelvis and hands, bone densitometry (DXA) and non-contrast cardiac CT for Agatston score (time 1). Continuous variables are presented as medians and categorical variables as frequencies. Associations between variables were performed using Wilcoxon matched-pairs test and Spearman correlation test. STATA software was used and p &lt; 0.05 was considered statistically significant.

Results
We recruited 85 patients from 1st October 2015 to 1st March 2018. At the end of 12 months, 6 patients refuse to perform the 2nd evaluation, 5 had primary non-function of the kidney graft, 1 had no 1st bone biopsy sample in time 0 and 4 patients died. We performed a 2nd evaluation in 69 patients and included those in this study.
Mean age 50.2±12.4 years, 48 men, 53 caucasian (78.8%), median BMI 24.5 (22.7 – 27.8), median dialysis vintage 55 months (42 – 84). Patients had a median cumulative steroid dose of 5692.5 (5260 – 7250) mg. At 12 months, the median FRAX value for osteoporotic fracture was 3.5 (2.2 – 6.2) and for femoral neck fracture was 0.8 (0.2 – 2.7). The DXA findings are shown in Table 1.
We found a negative correlation between vascular calcifications (Agatston Score and respective calcium percentile) and T and Z score of femoral neck (p=0.04), but not with the other DXA variables. Total femur variables (DMO, T-score, Z-score) were correlated with sclerostin values in time 1 (p&lt;0.01), and there was a trend for correlation between the spine DXA variables (DMO, T-score, Z-score) and sclerostin in time 1 (p=0.08, p=0.07, p=0.04). Spine DXA variables were negatively associated with alpha-klotho in time 0 (p=0.04, p=0.05, p=0.06). We didn’t found correlations with Pi, Ca or bAP. There was a negative correlation between FRAX osteoporotic and femoral neck fracture values and alpha-klotho in time 1 (p=0.002; p=0.003).

Conclusion
We found an inverse correlation between T and Z scores of femoral neck and coronary vascular calcifications. Regarding bone-derived hormones, Spine T and Z scores and FRAX values negatively correlated with alfa-klotho. Sclerostin seems to be associated with high mineral density.