P115 Quantitative MRI of muscles is different in rheumatoid arthritis patients compared to healthy controls
Authors: Farrow Matthew , Biglands John , Tanner Steven , Hensor Elizabeth , Buch Maya , Emery Paul , Tan Ai Lyn 
Published: April 2020

Abstract

Background
Rheumatoid arthritis (RA) can present with the loss of muscle mass and a decrease in strength and functional capability. Quantitative MRI offers a non-invasive measurement of muscle status which could improve the understanding of muscle pathology in RA. The purpose of this study was to assess whether MRI-based measurements of T2, fat fraction (FF), diffusion tensor imaging and muscle volume can detect differences between the muscles of RA patients and healthy controls in the thigh; and to assess how different stages of the disease present differently.

Methods
39 RA patients were recruited, comprised of 3 groups: 13 newly diagnosed treatment naïve (Group 1 - New RA: 10/13 female, mean age 63 years, mean CRP 31.5, mean EMS 71 minutes), 13 in clinical remission DAS28 &lt;2.6 for at least 1 year (Group 2 - Remission RA: 10/13 female, mean age 67 years, mean CRP 12.1, mean disease 74 months, mean EMS 2 minutes), 13 RA with at least 1 year diagnosis, DAS28 &gt;3.2 ± raised CRP/ESR ± DMARD/targeted therapy escalation ± requiring steroid therapy (Group 3 - Resistant RA: 10/13 female, mean age 65, mean CRP 17.4, mean disease 123 months, mean EMS 63 minutes). 13 healthy controls were also recruited. All 4 groups were age and gender matched. MRI of the dominant thigh was performed using a STEAM-EPI imaging sequence to assess diffusion: mean diffusivity (MD) and fractional anisotropy (FA), 2-point Dixon imaging to assess FF and a fat-suppressed turbo-spin echo sequence to measure T2. All participants had knee extension/flexion and grip strength torque measured using isokinetic dynamometer.

Results
A one-way ANOVA analysis demonstrated significant differences in T2, FF and muscle volume between RA patients and healthy controls, but no difference in MD or FA. There was no significant difference between the RA groups. T2 and FF were higher in RA patients whilst muscle volume was lower. Muscle volume was significantly correlated with early morning stiffness (rs = 0.4, p = 0.001), DAS28 (rs = 0.4, p = 0.001) and grip strength (rs = 0.5, p &lt; 0.001). All RA patients showed weaker strength compared to the healthy controls. Although the patients in remission (group 2) had better results compared to New (group 1) and Resistant RA patients (group 3), they performed worse than the healthy controls in all strength assessments.

Conclusion
Quantitative MRI can detect changes in the muscles of RA patients, whether they are newly diagnosed, in remission or with persistently active disease. Difference in T2, FF and muscle volume were apparent even at diagnosis, suggesting muscle changes in RA occur early. Despite effective RA therapy, patients in remission show worse MRI parameters and strength compared to healthy individuals. These warrant attention in improving the muscle strength and quality throughout the spectrum of the RA continuum.

Disclosures
M. Farrow: None. J. Biglands: None. S. Tanner: None. E. Hensor: None. M. Buch: None. P. Emery: None. A. Tan: None.