Assessment of muscle mass using chest computed tomography-based quantitative and qualitative measurements in patients with systemic sclerosis: A retrospective study with cross-sectional and longitudinal analyses.

BACKGROUND/ PURPOSE: Sarcopenia has been increasingly studied in systemic sclerosis (SSc), which is one of the most lethal autoimmune diseases, mainly due to lung involvement. Our objective was to study the associations of myopenia and/or myosteatosis with clinical features of SSc and subsequent adverse outcomes. METHODS: This is a retrospective study with cross-sectional and longitudinal analyses, in which patients with SSc were consecutively included in the outpatient clinic of a tertiary university hospital between 2012 and 2021. Clinical and laboratory parameters of patients with SSc were collected from their medical records. Skeletal muscle mass was assessed on chest computed tomography (CT) at the level of the first lumbar vertebra (L1) by skeletal muscle area (SMA), skeletal muscle index ([SMI] SMA/height2), and skeletal muscle radiation attenuation (SMRA). Cut-off values for myopenia in women and men were SMA <70.1 cm² and <110.4 cm², and SMI <25.9 cm²/m² and <34.6 cm²/m², respectively; values for myosteatosis in women and men were SMRA <29.8 HU and <36.3 HU, respectively. In a subgroup of 31 patients followed-up between 2017 and 2019, the diagnostic properties of SMA, SMI, and SMRA by CT were compared with the appendicular skeletal muscle mass index (ASMI) by dual-energy X-ray absorptiometry (DXA). Low muscle quantity was defined according to the European Working Group on Sarcopenia in Older People 2: ASMI <5.5 kg/m2 in women and <7.0 kg/m2 in men. Afterwards, a better tomographic index was used for correlating with clinical and laboratory parameters. RESULTS: Myopenia and/or myosteatosis were present in 75.7 % of patients with SSc. The prevalence rates according to each index were SMA 25.2%, SMI 12.1%, and SMRA 69.2%. In 73% of the patients with overweight/obesity (body mass index [BMI] ≥25 kg/m²), only SMRA was reduced. Considering ASMI as the gold standard, the sensitivity, specificity, positive and negative predictive values for SMA were 60%, 96.2%, 75% and 92.6%, respectively; for SMI, they were 40%, 96.2%, 66.7%, and 89.3%, respectively; for SMRA, these values were 60%, 34.6%, 15%, and 81.8%. Pearson's correlation coefficients were 0.73, 0.74, and 0.10 for SMA, SMI, and SMRA, respectively, and ASMI significantly agreed with SMA (kappa 0.611, p < 0.001) and SMI (kappa 0.431, p = 0.012). After adjustments in a multivariate model, BMI (p < 0.001) and female sex (p < 0.001) remained significantly associated with myopenia by SMA; BMI (p =0.010) remained significantly associated with low muscle mass by ASMI. CONCLUSION: The SMA index at L1 level on chest CT was demonstrated to be an accurate measure that is useful for detecting myopenia in patients with SSc. BMI and male sex predicted low SMA and BMI was associated with low ASMI on DXA. STATEMENT OF CLINICAL SIGNIFICANCE: In recent years, great advances have been made in sarcopenia-related research, resulting in broader knowledge on its definition, causes, diagnosis, and treatment options. Regarding the techniques used for assessing muscle composition, computed tomography (CT) was demonstrated by many studies to be an efficient and easy-to-use method that can be employed by professionals of different specialties, including rheumatologists. This study was able to demonstrate that although the L3 image was not present on CT, the analysis of SMA at the L1 level on chest CT proved to be an accurate and useful measure to detect myopenia in patients with SSc. This study identified some associated factors of myopenia and/or myosteatosis according to each method employed for assessing muscle composition. Reduced BMI and male sex were associated factors of myopenia when using SMA, and reduced BMI was associated with myopenia when employing ASMI by DXA. Finally, we highlight the need not to generalize the term "sarcopenia" in clinical studies assessing imaging parameters of body composition. The use of the terms myopenia and/or myosteatosis would be more adequate, because CT allows the assessment of muscle composition and not strength or physical performance.

Physical frailty in patients with systemic sclerosis.

INTRODUCTION: Systemic sclerosis (SSc) is a chronic disease characterized by autoimmunity, vasculopathy and fibrosis of several organs, such as skin, lungs, and heart. During the disease course, patients with SSc are prone to accumulating multiple organ damage and increasing their vulnerability to adverse outcomes. This increased vulnerability to adverse outcomes when exposed to a stressor among people of the same age is known as frailty. One of the most used definitions of frailty is the physical frailty phenotype (PFP), including 5 components: unintentional weight loss, exhaustion, muscle weakness, slow walking speed, and low physical activity. There is scarce data about frailty in patients with SSc. OBJECTIVES: To determine the prevalence and clinical profile of PFP in a sample of patients with SSc. To investigate the diagnostic accuracy of the Fatigue, Resistance, Ambulation, Illness and Loss of weight (FRAIL) scale, Edmonton frailty scale (EFS) and Short Physical Performance Battery (SPPB) using the PFP as the reference standard. METHODS: Cross-sectional study including 94 patients with SSc according to the 2013 ACR-EULAR classification criteria or the criteria suggested by Le Roy and Medsger for early disease. Gastrointestinal symptoms were assessed by the UCLA GIT 2.0 questionnaire, malnutrition was defined according to European Society of Clinical Nutrition and Metabolism (ESPEN) recommendations, and physical performance was assessed by SPPB. PFP assessment was according to the original definition, except for physical activity domain, assessed with the International Physical Activity Questionnaire (IPAQ). FRAIL scale and EFS were also applied to the same individuals. For diagnostic assessment of FRAIL, EFS and SPPB, we estimated the area under the receiver operating characteristic curve (AUC), considering PFP as the reference standard and dichotomizing the results in frail vs. non-frail. RESULTS: According to PFP, 33 patients (35.1%) were considered frail and 53 patients (56.4%) pre-frail. According to FRAIL scale, 27 patients (28.7%) were considered frail and 53 patients (56.4%) pre-frail. According to EFS, 28 patients (29.7%) were classified as vulnerable and 15 (15.9%) as frail: mild in 8 (8.5%), moderate in 5 (5.3%) and severe in 2 (2.1%). According to SPPB, 19 patients (20.2%) were considered frail. The AUC against PFP was: 0.829 (95% CI 0.743-0.916) for FRAIL scale, 0.859 (95% CI 0.784-0.934) for EFS and 0.791 (95% CI 0.697-0.885) for SPPB. The PFP was associated with current use of glucocorticoids (p=0.011), UCLA GIT 2.0 score (p=0.001), HAQ (p<0.0001), patient and physician-assigned VAS (p<0.0001, both), malnutrition (p=0.007), hospitalizations in the past year (p=0.008) and dependence on BADL and IADL (p=0.027 and p<0.0001, respectively). The PFP was not associated with gender (p=0.679), age (p=0.303), disease duration (p=0.504), Rodnan skin score (p=0.918), diffuse subtype (p=0.116), polypharmacy (p=845) and sarcopenia (p=0.328). CONCLUSION: Frailty is prevalent in patients with long-standing SSc and is associated with disability, limitations in daily activities and hospitalizations in the past year. Also, malnutrition and more severe gastrointestinal symptoms were more common in frail patients. Both FRAIL scale and EFS showed excellent diagnostic accuracy against PFP as the reference standard, however the FRAIL scale presents a higher sensitivity and seems to be more feasible and practical than EFS and SPPB in clinical practice.