P.21.9 Responsiveness of muscle testing and functions in a retrospective 51 inflammatory myopathies patient series

Abstract

Some criteria have been developed to assess muscle strength in inflammatory myopathies, but with no consensus. We evaluated at baseline and 6 month later severely affected patients (excluding inclusion body myositis) who required a treatment combining steroids (at least 1 mg/kg), methotrexate, azathioprine or cyclophosphamide and intravenous immunoglobulins. We assessed by MRC testing: neck flexors, upper arm abductors, elbow flexors, hip flexors, knee extensors and flexors, and gluteus medius. We also recorded Barre and Mingazzini tests and CK level. Responsiveness of muscle testing was assessed with the calculation of Standardized Response Mean (SRM), and Effect Size (ES). Values of 0.8 were considered as small, moderate and large responsiveness, respectively. We included 51 patients (mean age 46.3), including 19 overlap myositis (OM, mostly anti-synthetase syndrome), 14 dermatomyositis (DM), and 18 necrotizing auto-immune myopathies (NAM). Baseline CK was 5533 ± 10798 U/L. OM and DM patients had a very close clinical presentation, while NAM had a poorer Mingazzini test (31.3, 37.7 and 10.1 s, respectively, p = 0.04) with a lower hip flexors testing (median: 3.5, 4, and 2, respectively, p = 0.003). Highest responsiveness was observed for hip flexors testing (SRM: 1.25, ES: 0.99), upper arm abductors (SRM: 1.11, ES: 0.99), elbow flexion (SRM: 0.96, ES: 0.91), and neck flexion (SRM: 0.89, ES: 0.82). Other muscular groups testing showed a moderate responsiveness, with knee extensors showing the weakest one (SRM: 0.51, ES: 0.53). CK level had a small responsiveness (mean decrease: −5208 UI/L, SRM: 0.48, ES: 0.48). Mingazzini and Barre’s tests had a noticeably large responsiveness (Barre: SRM: 1.01, ES: 0.78, Mingazzini: SRM: 0.89, ES: 0.2). When assessing myositis, responsive testing such as hip flexors and upper arm abductors testing should be preferred. Some simple clinical tests such as Barre and Mingazzini’s tests could also be an aid.