FRI0494 CORRELATION OF METACARPAL BONE MASS MEASURED EITHER BY DUAL X-RAY DENSITOMETRY OR DIGITAL X-RAY RADIOGRAMMETRY WITH SEVERITY OUTCOMES IN PATIENTS WITH EARLY ARTHRITIS
Authors: Irene Llorente, Saturnino Gonzalez, Eugenio Escolano, Ana Maria Ortiz, Alberto García-Vadillo, Isidoro González-Álvaro, Santos Castañeda
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Rheumatoid arthritis (RA) is a systemic autoimmune disorder that predominantly affects small joints of the hands and feet. X-ray digital radiogrammetry (DXR) is a validated technique for the evaluation of bone mineral density (BMD) in the diaphysis of metacarpals (MC) that has demonstrated that low bone mass at this location correlates with worse radiographic progression (1). However, this technique is not available in our environment. Dual X-ray densitometry (DXA) is a simple, accessible and widely validated technique for the study of osteoporosis. Our group has previously validated the reproducibility of MCP measurements by DXA (2). <h3>Objectives</h3> To study the relationship between baseline MC BMD measured by DXA or DXR and disease severity in patients with early arthritis at 2 years follow-up. <h3>Methods</h3> 202 patients belonging to PEARL (Princess Early Arthritis register longitudinal) study were included. Demographic, laboratory, radiographic and therapeutic data were recorded by protocol. Most patients (87%) were women, 59% fulfilled 2010 ACR criteria and 41% were classified as undifferentiated arthritis. More than 60% were seropositive (60% RF; 58% anti-CCP). Median disease duration at first visit was 4.6 months, median DAS28 4.2 and HAQ 0.875. The BMD of 2th to 4<sup>th</sup> MC was measured by DXR through the standardized software by Sectra (Linköping, Sweden) applied on radiographs of hands submitted in digital format (GE© DX Definium 8000). Baseline non-dominant hand DXA was performed using a densitometer Hologic© QDR4500. To analyze 2<sup>th</sup> to 4<sup>th</sup> MC BMD, we created 3 regions of interest (ROI) similar to that generated in the DXR measurements; briefly, the ROIs cover the mid-third of each MC diaphysis, avoiding overlapping of ROIs. The statistical study was performed with Stata 12 for Windows, including linear correlation between MC-BMD values measured by DXR and DXA (Pearson's test), and different multivariate analyses in which MC-BMD measured either by DXR or DXA were included as dependent variable and sex, age and body mass index (BMI) as independent confounding variables. Then in these models different subrogate variables of disease severity such as disease activity (DAS28), disability (HAQ) or cumulative DMARD treatment after 2 years of follow-up were included in order to determine whether there was an association with MC-BMD. <h3>Results</h3> The MC-BMD measured by DXA and DXR at baseline showed a good correlation (r=0.87, p &lt;0.001). As expected, being female (ß coefficient -0.0381, p=0.0001) and age &gt; 65 years (ß coefficient -0.076, p=0.0001) were associated with lower BMD, whereas high body mass index (ß coefficient 0.002 x kg/m<sup>2</sup>, p=0.004) was associated with higher BMD. Adjusting by this confounding variables, the multivariate analyses did not show any significant association between MC-BMD and DAS28, HAQ or treatment intensity, neither with the DXA or DXR measurements. <h3>Conclusion</h3> Despite of the good correlation between DXR and DXA, our data obtained either with DXA or DXR do not confirm the association of low MC-BMD measured with DXR and more aggressive disease in patients with early arthritis. <h3>References</h3> [1] Forslind K, Boonen A, Albertsson K, et al. Scand J Rheumatol2009;38:431-438. [2] Castañeda S, González-Álvaro I, Rodríguez-Salvanés F, et al. J Clin Densitom2007;10:298-305. <h3>Acknowledgement</h3> We would like to thank Teresa Velasco, nurse of the Rheumatology Division, for her invaluable help in the Early Arthritis Clinic <h3>Disclosure of Interests</h3> Irene Llorente : None declared, Saturnino Gonzalez: None declared, Eugenio Escolano: None declared, Ana Maria Ortiz: None declared, Alberto García-Vadillo: None declared, Isidoro González-Álvaro: None declared, Santos Castañeda Consultant for: Amgen, BMS, Pfizer, Lilly, MSD, Roche, Sanofi, UCB