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

Abstract

BackgroundRheumatoid 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).ObjectivesTo 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.Methods202 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 4th 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 2th to 4th 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.ResultsThe MC-BMD measured by DXA and DXR at baseline showed a good correlation (r=0.87, p <0.001). As expected, being female (ß coefficient -0.0381, p=0.0001) and age > 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/m2, 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.ConclusionDespite 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...

Osteoporosis in Rheumatoid Arthritis: Dangerous Liaisons

“…On the contrary, conventional dual X-ray densitometry (DXA) is the gold standard for assessing BMD in OP, and is also a simple and more accessible technique all over the world. Of note, our group has recently proved that measurement of BMD at metacarpal diaphysis with conventional DXA is reproducible and closely correlates with DXR measurements (87,88).…”