Objective To investigate the association of low-density (lipid-rich) muscle measured by computed tomography (CT) with skeletal muscle function and health-related quality of life in idiopathic inflammatory myopathies (IIMs). Methods Seventeen patients and ten healthy controls underwent CT of the mid-thigh to quantify high (30-100HU) and low density (0-29HU) skeletal muscle areas. Anthropometric measures, body composition, physical activity level, health-related quality of life, skeletal muscle strength, endurance and fatigue were assessed. Patients were compared against controls. The relationship of anthropometric, body composition and disease variables with measures of muscle function were examined using Spearman’s test on the patient group. Linear regression was used to assess the age-and disease-adjusted relationship of muscle quality to physical function and muscle strength. Results Patients had higher body fat% (p=0.042), trunk fat mass (p=0.042), android/gynoid fat (p=0.033) and mid-thigh low density muscle/total muscle area (p<0.001) compared to controls. Mid-thigh low density muscle/total muscle area was negatively correlated with self-reported physical function, strength and endurance; the SF-36 physical functioning (p=0.004), manual muscle testing (p=0.020), knee maximal voluntary isometric contraction/thigh mineral free lean mass (p<0.001) and the endurance step test (p<0.001), suggesting that muscle quality impacts function in IIM. Using multiple linear regression adjusted for age, global disease damage, and total fat mass, poor muscle quality as measured by mid-thigh low density muscle/total muscle area was negatively associated with SF-36 physical functioning (p= 0.009). Conclusion Mid-thigh low density muscle/ total muscle area is a good predictor of muscle strength, endurance and health-related quality of life as it pertains to physical functioning in patients with IIMs.

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Objective The goals of this study were to assess the predictive value of chart abstracted American College of Rheumatology-Functional Status (ACR-FS) with patient reported ACR-FS, and to relate them with measures of muscle function in a single institution cohort of patients with idiopathic inflammatory myopathies (IIMs). Methods Demographic and clinical data on 102 patients with IIMs regularly followed in the Rheumatology and Neurology Clinics at the University of Kentucky Medical Center between 2006 and 2012 were obtained through retrospective chart review. Clinical and functional status evaluation, muscle performance testing, and body composition measures were performed on a subset of 21 patients. ACR-FS were obtained both by chart abstraction and direct patient report. Spearman’s correlations were used to examine the relationship of ACR-FS derived from chart abstraction with direct patient report, as well as the relationship of measures of physical function and body composition with ACR-FS. Results ACR-FS derived from chart abstraction was significantly correlated with ACR-FS derived from direct patient report (ρ=0.78, p<0.001). ACR-FS derived from chart abstraction was also significantly correlated with patient reported physical function (ρ= −0.71, p<0.001) and physical activity (ρ=−0.58, p<0.05), manual muscle testing (ρ= −0.66, p<0.01) and skeletal muscle endurance as measured by the functional index-2 test (shoulder flexion ρ= −0.62, p<0.01; hip flexion ρ= −0.65, p<0.0; heel lift ρ= −0.67, p<0.01; and toe lift ρ= −0.68, p<0.01). Conclusion The ACR-FS is a simple measure of disability that can be used in chart abstraction studies involving IIM patients. We have demonstrated that ACR-FS correlates well with muscle performance tests of strength and endurance.

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Background Many patients with IIMs exibit chronic muscle weakness and functional disability despite treatment. In polymyositis/ dermatomyositis (PM/DM), male sex, higher prednisone dosage and older age have been associated with muscle weakness and functional disability.[1,2] Sporadic inclusion body myositis (sIBM) itself is associated with major end-stage disability.[3] The ACR functional status (ACRFS) criteria have been used as a core measure of the consequences of impairment in IIM.[4] However, its association with known or suspected risk factors of disability warrants further investigation. Objectives To determine predictors of current/ worst ever ACRFS with known or suspected risk factors of disability and muscle weakness in patients with IIM. Methods Data were obtained from chart reviews of IIM and overlap myositis (OM) cases seen in the Rheumatology and Neurology Clinics at the University of Kentucky from May/06 until July/12. Current and worst ever ACRFS, demographic and clinical characteristics were abstracted from medical records. One-way ANOVA and Fisher’s exact/ Chi-square tests were used to compare groups on continuous/ categorical variables, respectively. Ordinal logistic regression was applied to estimate the effects of IIM type, age, sex and disease duration from diagnosis on current and worst ever ACRFS. Results 90 patients with IIM and OM were included: 38 PM, 29 DM, 12 IBM and 11 OM. When patient ages were divided into tertiles, sIBM patients were significantly older (p= 0.03). Females predominated in the PM, DM and OM groups. In sIBM, females were slightly outnumbered. Mean duration of disease from diagnosis was highest in sIBM (73 mo) compared to PM (39 mo), DM (18 mo) and OM (35 mo) (p=0.01). sIBM was more likely to be associated with presence of some degree of disability at the last time of assessment (91%), compared to all other groups combined (73%) (p=0.001). In the multivariable analysis, poorer current ACRFS and worst ever ACRFS were independently associated with higher age, and higher age and longer disease duration, respectively, controlling for all other variables. Conclusions The demographic and clinical characteristics of our cohort are consistent with previous reports. As expected, sIBM was associated with increased odds of disability. In the multivariate analysis, higher age and disease duration were identified as independent risk factors for disability. References Bronner IM, Van Der Meulen MF, De Visser M et al. Long-term outcome in polymyositis and dermatomyositis. Annals of the rheumatic diseases 65(11), 1456-1461 (2006). Clarke AE, Bloch DA, Medsger TA, Jr., Oddis CV. A longitudinal study of functional disability in a national cohort of patients with polymyositis/dermatomyositis. Arthritis and rheumatism 38(9), 1218-1224 (1995). Cox FM, Titulaer MJ, Sont JK, Wintzen AR, Verschuuren JJ, Badrising UA. A 12-year follow-up in sporadic inclusion body myositis: an end stage with major disabilities. Brain : a journal of neurology 134(Pt 11), 3167-3175 (2011). Stucki G...