Performance of CT Parameters Compared to Bone Mineral Density to Detect Bone Fragility in Rheumatoid Arthritis

Objective: To evaluate the performance of CT parameters (SBAC-L1 and fractal analysis) compared to BMD (gold standard) to detect vertebral fractures in rheumatoid arthritis

To evaluate the performance of scanographic bone attenuation coefficient of the first lumbar vertebra (SBAC-L1) and fractal analysis, markers of bone fragility on computed tomography (CT), compared to bone mineral density (BMD) to detect vertebral fractures in rheumatoid arthritis (RA). Patient and methods: Rheumatoid arthritis patients followed from 2009 to 2019 in Nancy University hospital who met the 2010 ACR/EULAR criteria for RA and examined using thoraco-abdomino-pelvic CT (TAP-CT) and BMD (spine, hip) within a period of up to 2 years were included. Scanographic bone attenuation coefficient and fractal dimension of the first lumbar vertebra (SBAC-L1, FD-L1) were measured on CT. Vertebral fractures of the thoracolumbar spine were evaluated on CT according to an adaptation of Genant's scoring method. Demographic characteristics (age, sex, smoking), clinical data (disease duration, DAS-28), biological data (C-reactive protein (CRP), RF, ACPA) and treatments (n proton pump inhibitor, corticosteroid, TNF-inhibitors (TNFi) and others biologics, calcium, vitamin D, antiresorptive agents) were collected from the complete medical record. Univariate and multivariate analysis were performed to determine if these variables were associated or not with bone fragility (vertebral fracture, SBAC-L1, FD-L1). We evaluated the performance and diagnostic complementarity as well as optimal diagnostic thresholds of SBAC-L1, FD-L1 and BMD (gold standard) to detect vertebral fractures in these patients at risk of osteoporosis. Intra and inter-readers reproducibilities of the scanographic screening methods (SBAC-L1, FD-L1) were also studied.