Background Inflammatory rheumatic diseases such as rheumatoid arthritis (RA) or ankylosing spondylitis (AS) are associated with osteoporosis and increased risk of fractures. This bone involvement is related to the inflammatory process, the treatments given such as corticosteroids (CTC) and the menopausal status. Bone mass in RA and AS has been well evaluated by measuring areal bone mineral density (BMD) with DXA. Trabecular bone score (TBS) is a new method evaluating bone microarchitecture by assessing pixel gray- level variations in DXA images from lumbar spine. The clinical usefulness of this method is currently being evaluated in post menopausal osteoporosis.
Objectives to evaluate TBS in patients with RA or AS and to compare these results with spine BMD measurements.
Methods 30 patients with RA (ACR criteria, 19 F; 12 post menopausal women; age [mean ± SD]: 56.9±9.7 years; disease duration: 11.7±8.8 years; 26 under low dosage CTC) and 31 patients with AS (modified NY criteria, 28 M, age 43.8±13.4; disease duration: 13.0±11.1; no CTC) were evaluated and compared to 51 healthy subjects (29 F, 12 post menopausal women, age: 46.6±11.1). L2-L4 spine BMD and hip BMD were measured using DXA (Lunar, iDXA). TBS was calculated from L2-L4 BMD images (TBS insight®, Med-Imaps).
Results compared to healthy subjects, patients with RA and AS had elevated biological markers of inflammation (ESR, CRP, IL-6) (all p<0.0001). RA patients had decreased BMD and T score at the hip (p<0.005) compared to the control group. Hip T score in patients with AS was also decreased (p=0.02). The other BMD measurements (L2-L4 BMD, total body BMD) did not differ between the patients and the controls. TBS was decreased in RA and AS compared to healthy subjects: 1.242±0.16 vs 1.282±0.13 vs 1.365±0.14, respectively (p=0.005). In the whole population, TBS correlated with spine BMD measurements (r=0.29, p=0.002). In AS, we observed no correlation between TBS and biological or clinical indexes of disease activity while in RA, IL-6 correlated with TBS (r =0.44, p=0.02). We also examined TBS results according to male/female distribution in RA and AS and confirmed that TBS was decreased in both women and men with RA while TBS did not differ between male AS and male controls.
Conclusions in this study, we observed decreased TBS values, mainly in patients with RA, suggesting that bone micro architecture is altered in RA, and this may probably be related to CTC treatment. In addition, TBS analysis may found decreased values whereas areal BMD measurements are normal, suggesting a potential interest of this new method in evaluating bone status in inflammatory rheumatic diseases.
Disclosure of Interest None Declared
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