SAT0449 SPONDYLOARTHRITIS AND FRACTURE RISK: DOES DXA REALLY HAVE AN IMPACT IN THE RISK OF FRACTURE ESTIMATED BY FRAX?
Authors: B. M. Fernandes, S. Garcia, S. Ganhão, M. Rato, F. Pinheiro, M. Bernardes, L. Costa
Journal: Annals of the Rheumatic Diseases (2020)

Background: Low bone mineral density (BMD) is common in ankylosing spondylitis (AS). The fracture risk (FR) is increased and its reduction with pharmacologic therapy is not clearly defined in this population. However, early screening and bisphosphonates as first-line treatment are recommended. Objectives: To investigate the influence of dual-energy X-ray absorptiometry (DXA) in the ten-year risk of fracture assessed by FR Assessment Tool (FRAX) and to determine possible demographic or clinical factors associated with an increased FR in a spondyloarthritis (SpA) population. Methods: Retrospective study including all the over 40 years-old SpA patients (ASAS classification criteria) followed at our Rheumatology Department and registered in the national database. Demographic, clinical and laboratorial data were collected at the time of the last follow-up visit. Data from the last DXA (until 3 years prior to the last visit) were collected. Indication for pharmacological treatment by FRAX was assessed according to the national recommendations. Results: A total of 231 SpA patients were included: 126 males (54.5%), 53 (22.9%) smokers; 171 (74%) had AS, 23 (10%) had Inflammatory Bowel Disease Associated SpA and 37 (16%) had Undifferentiated SpA. At the last follow-up visit, the mean age was 52.9 years (±9.6) and the median disease duration was 21.9 years [1.0-55.5]. The mean ASDAS-CRP was 2.5 (±0.9) and the majority of patients had moderate (25.5%) or high (48.5%) disease activity (according to ASDAS). One hundred and thirty patients (56.3%) were taking NSAIDs, 45 (19.5%) were taking glucocorticoids, 85 (36.8%) were under csDMARDs and 170 (73.6%) under bDMARDs [157 (68%) under TNFi, 11 (4.8%) under secukinumab and 2 (0.9%) under ustekinumab]. Eleven patients (4.8%) had previous fragility fractures, 118 (51.1%) had DXA in the last 3 years and 167 (72.3%) were taking calcium and/or vitamin D supplements. Sixteen patients (6.9%) had indication for treatment by FRAX without DXA and 9 of these (56.3%) were already under treatment. Similarly, 16 (6.9%) had indication for treatment by FRAX with DXA and 13 of these (81.3%) were already under treatment. Ten patients (4.3%) were reclassified in FRAX with DXA: 7 (3%) had no indication for treatment by FRAX without DXA but obtained it by FRAX with DXA and 3 (1.3%) had indication for treatment by FRAX without DXA but they lost it by FRAX with DXA. We found a moderate level of agreement in the indication for treatment between FRAX with and without DXA (kappa=0.595; p&lt;0.001). The use of DXA in FRAX estimated a significant higher median FR, both for major osteoporotic fracture (2.4% [0.8-31.0] vs 1.8% [0.6-20.0]; p&lt;0.001) and for hip fracture (0.5% [0.0-23.0] vs 0.2% [0.0-14.0]; p&lt;0.001). We found significant correlations between FR and some disease-related variables (table 1). Table 1. Correlations between the risk of fracture estimated by FRAX and disease-related variables. Disease duration BASDAI ASDAS-CRP BASMI BASFI Estimated fracture risk by FRAX: without DXA major osteoporotic fracture r=0.352 p &lt;0.001 r=0.204 p =0.002 r=0.214 p =0.001 r=0.301 p &lt;0.001 r=0.317 p &lt;0.001 hip fracture r=0.389 p &lt;0.001 r=0.142 p =0.034 r=0.170 p =0.011 r=0.305 p &lt;0.001 r=0.275 p &lt;0.001 with DXA major osteoporotic fracture r=0.227 p =0.014 r=0.314 p =0.001 r=0.356 p &lt;0.001 r=0.293 p =0.002 r=0.379 p &lt;0.001 hip fracture n.s. r=0.197 p =0.036 r=0.269 p =0.004 r=0.271 p =0.004 r=0.258 p =0.006 Conclusion: Our results showed that a similar number of patients had indication for pharmacological treatment by FRAX both with and without DXA. Although the inclusion of DXA resulted in a higher estimated FR by FRAX, the observed moderate level of agreement between FRAX with and without DXA suggests that the FR estimation by FRAX, even without DXA, may be a reasonable approach in SpA patients. In line with literature, we found significant associations between the estimated risk fracture by FRAX and some disease activity and function measures. Disclosure of Interests: Bruno Miguel Fernandes: None declared, Salomé Garcia: None declared, Sara Ganhão: None declared, Maria Rato: None declared, Filipe Pinheiro: None declared, Miguel Bernardes Speakers bureau: Abbvie, Amgen, Biogen, Eli-Lilly, Glaxo-Smith-Kline, Pfizer, Janssen, Novartis, Lúcia Costa: None declared