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.

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. 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. 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. 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. 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.

da Rocha DS ，Tessari JA ，Mainardi NB ，Hax V ，Gasparin AA ，de Oliveira CAV ，Garcia TS ，Xavier RM ，Chakr RMDS ... -  《-》

Feasibility of using chest computed tomography (CT) imaging at the first lumbar vertebra (L1) level to assess skeletal muscle mass: a retrospective study.

Liu S ，Han X ，Li J ，Xie X ，Yang Y ，Jiang W ，Liu L ，Liu Z ... -  《PeerJ》

Skeletal muscle cutoff values for sarcopenia diagnosis using T10 to L5 measurements in a healthy US population.

Derstine BA ，Holcombe SA ，Ross BE ，Wang NC ，Su GL ，Wang SC ... -  《Scientific Reports》

Relative muscle indices and healthy reference values for sarcopenia assessment using T10 through L5 computed tomography skeletal muscle area.

Derstine BA ，Holcombe SA ，Wang NC ，Ross BE ，Sullivan JA ，Wang SC ，Su GL ... -  《Scientific Reports》

Normative values of skeletal muscle indices for nutritional assessment and implications on definition of sarcopenia in Indian adult population.

Sarcopenia is defined as both low muscle function (performance or strength) and low muscle mass. Although aging is the main cause of sarcopenia, it can also occur due to poor nutrition and chronic diseases like liver cirrhosis, chronic kidney disease, and diabetes. To do the quantitative analysis of various normative skeletal muscle indices (to define sarcopenia) in the Indian population. Sex-specific means, standard deviations (SD), and sarcopenia cutoffs (mean-2SD) of psoas muscle thickness (PMTH), psoas muscle area (PMA), psoas muscle index (PMI), erector spinae muscle area (ESMA), skeletal muscle radiation attenuation (SMRA), total skeletal muscle area (SMA), and total skeletal muscle index (SMI) were computed. A total of 2002 individuals (1308 males and 694 females) underwent CT evaluation. PMTH (mm/m) was observed to be 15.87±2.67 in males vs. 12.61±2.46 in females (p=0.0001); PMA (cm2) was 18.55±3.45 in males vs.13.52±2.80 in females (p=0.0001); PMI (cm2/m2) was 6.69±1.40 in males vs. 5.57±1.18 in females (p=0.0001); ESMA (cm2) was 45.74±6.01 in males vs. 35.37±5.63 in females (p=0.0001); ESMI (cm2/m2) was 16.5±2.55 in males vs. 14.62±2.6 in females (p=0.0001); SMRA was 55.80±3.91 Hounsfield unit (HU) in males vs. 52.36±3.67 HU in females (p=0.0001); SMA (cm2) was 147.73±11.77 in males vs. 106.33±12.00 in females (p=0.0001); and SMI (cm2/m2) was estimated to be 51.00±5.70 in males vs. 43.93±6.05 in females (p=0.0001). PMTH, PMI, ESMI, SMI, and SMRA cutoffs for sarcopenia at L3 were observed to be 10.53 mm/m, 3.89 cm2/m2, 11.40 cm2/m2, 39.59 cm2/m2, and 47.98 HU among males and 7.69, 3.20, 9.42, 31.83, and 45.01 among females, respectively; these values were consistent with previously reported cutoffs in Indian studies but not consistent with the cutoffs reported in other countries. Normative values of skeletal muscle indices for either sex among the Indian adult population would enable future studies on sarcopenia in various medical conditions.

Choudhary S ，Wadhawan M ，Dhawan S ，Ganesan PK ，Mittal P ，Sahney A ，Kumar A ... -  《-》