Cut-off values of skeletal muscle index and psoas muscle index at L3 vertebra level by computerized tomography to assess low muscle mass.

Computerized tomography (CT) is considered the gold standard for the evaluation of total skeletal muscle quantity. Skeletal muscle assessments at the L3 vertebra level revealed significantly correlated with total body muscle measurements. Clinicians need cut-offs to evaluate low muscle mass in various patients who already had CT imaging without any additional cost. This assessment is important to help the physicians to stratify the patients for mortality and other complications. It may also enable the diagnosis of malnutrition by the GLIM criteria. Few studies reported cut-offs in different populations. We aimed to provide cut-off values for total skeletal muscle index (SMI) and psoas muscle mass index (PMI) at the L3 vertebra level in the Turkish population. We assessed the preoperative plain CT images of living adult liver donors who were admitted to a single transplantation center between June 2010 and April 2018. We derived cut-off values with two alternative methods, the 5th percentile value or mean minus two standard deviations and from two groups of study participants, i.e. the total study population and the younger subgroup aged between 18 and 40. The study population involved 601 subjects with a mean age of 32.5 ± 9 (range: 18-59 years) and 326 (54.2%) was male. The younger subgroup was composed of 482 individuals with a mean age of 28.8 ± 5.9 and 55.6% male. In patients aged between 18 and 40, PMI and SMI cut-offs by using the 5th percentile were 5.40 cm2/m2, 41.42 cm2/m2 for males; and 3.56 cm2/m2, 30.70 cm2/m2 for females; respectively. The cut-offs of PMI and SMI by using mean minus two standard deviations were 4.62 cm2/m2, 38.67 cm2/m2 for males; and 2.66 cm2/m2, 27.8 cm2/m2 for females; respectively. These cut-offs were comparable to the other populations. Our study provided cut-offs to be used in CT images for PMI and SMI. There is a need for further longitudinal studies to verify whether these cut-offs are successful in predicting mortality or other adverse outcomes associated with low muscle mass.

Bahat G ，Turkmen BO ，Aliyev S ，Catikkas NM ，Bakir B ，Karan MA ... -  《-》

Defining reference values for low skeletal muscle index at the L3 vertebra level based on computed tomography in healthy adults: A multicentre study.

Skeletal muscle mass loss is an important aspect of malnutrition and is closely related to adverse clinical outcomes. Computed tomography (CT) is the gold standard for analysing muscle mass, and the skeletal muscle index at the third lumbar vertebra (L3-SMI), measured using CT, is an important indicator to evaluate total skeletal tissue. The aims of this study were to establish reference values for low L3-SMI in Northern China, and to investigate the correlation between L3-SMI and age, and the correlation between L3-SMI and body mass index (BMI). This was a multicentre, retrospective, cross-sectional study. A search of abdominal CT imaging reports, using specific keywords, was conducted in four representative cities in northern China, from January 2016 to March 2021. Transverse CT images at the level of the third lumbar vertebra (L3) were identified, exported from the Radiology Information System, and measured using the analysis software SliceOmatic. Statistical analyses were performed using SPSS 24.0, and significance level was set at p < 0.05. Mean, standard deviations (SD) and percentiles (p5, p10, p25, p50, p75, p90, p95) were used to describe the distribution of L3-SMI in the study population. Low skeletal muscle index was defined as a 5% percentile, or two standard deviations below the mean value of younger healthy individuals (age 20-39 years). The study included 1787 healthy individuals, with a median age of 45 (25) years (range 20-88 years), and a median BMI of 23.1 (4.1) kg/m2 (range 18.5-38.7 kg/m2). Among them, 700 healthy individuals (39.1%) were aged 20-39 years. L3-SMI had a negative linear correlation with age, and a positive linear correlation with BMI. The L3-SMI reference values used to define low skeletal muscle mass loss in the Northern Chinese population, using the 5% percentile, were 40.2 cm2/m2 in men, and 31.6 cm2/m2 in women. Using the mean minus two standard deviations protocol, the reference values were 37.9 cm2/m2 and 28.6 cm2/m2 in men and women, respectively. This study analysed the human body composition of 1787 healthy people in four cities in northern China, using CT, and established diagnostic thresholds of skeletal muscle mass depletion based on 700 younger healthy adults, using the 5% percentile and mean-2SD methods. These reference values can be used to diagnose malnutrition in patients and may aide clinicians in predicting prognosis and improving nutritional therapy. Further research is warranted to determine the prognostic role of reference values against clinical outcomes in different disease populations.

Kong M ，Geng N ，Zhou Y ，Lin N ，Song W ，Xu M ，Li S ，Piao Y ，Han Z ，Guo R ，Yang C ，Luo N ，Wang Z ，Jiang M ，Wang L ，Qiu W ，Li J ，Shi D ，Li R ，Cheung EC ，Chen Y ，Duan Z ... -  《-》

Psoas muscle index is not representative of skeletal muscle index for evaluating cancer sarcopenia.

A common method for diagnosing sarcopenia involves estimating the muscle mass by computed tomography (CT) via measurements of the cross-sectional muscle area (CSMA) of all muscles at the third lumbar vertebra (L3) level. Recently, single-muscle measurements of the psoas major muscle at L3 have emerged as a surrogate for sarcopenia detection, but its reliability and accuracy remain to be demonstrated. This prospective cross-sectional study involved 29 healthcare establishments and recruited patients with metastatic cancers. The correlation between skeletal muscle index (SMI = CSMA of all muscles at L3/height2 , cm2 /m2 ) and psoas muscle index (PMI = CSMA of psoas at L3/height2 , cm2 /m2 ) was determined (Pearson's r). ROC curves were prepared based on SMI data from a development population (n = 488) to estimate suitable PMI thresholds. International low SMI cut-offs according to gender were studied for males (<55cm2 /m2 ) and for females (<39 cm2 /m2 ). Youden's index (J) and Cohen's kappa (κ) were calculated to estimate the test's accuracy and reliability. PMI cut-offs were validated in a validation population (n = 243) by estimating the percentage concordance of sarcopenia diagnoses with the SMI thresholds. Seven hundred and sixty-six patients were analysed (mean age 65.0 ± 11.8 years, 50.1% female). Low SMI prevalence was 69.1%. Correlation between the SMI and PMI for the entire population was 0.69 (n = 731, P < 0.01). PMI cut-offs for sarcopenia were estimated in the development population at <6.6cm2 /m2 in males and at <4.8 cm2 /m2 for females. The J and κ coefficients for PMI diagnostic tests were weak. The PMI cut-offs were tested in the validation population where 33.3% of the PMI measurements were dichotomously discordant. A diagnostic test employing single-muscle measurements of the psoas major muscle as a surrogate for sarcopenia detection was evaluated but found to be unreliable. The CSMA of all muscles must be considered for evaluating cancer sarcopenia at L3.

Pigneur F ，Di Palma M ，Raynard B ，Guibal A ，Cohen F ，Daidj N ，Aziza R ，El Hajjam M ，Louis G ，Goldwasser F ，Deluche E ... -  《-》

Poor performance of psoas muscle index for identification of patients with higher waitlist mortality risk in cirrhosis.

Sarcopenia, characterized by low muscle mass, associates with mortality in patients with cirrhosis. Skeletal muscle area in a single computed tomography image at the level of the third lumbar vertebrate (L3) is a valid representative of whole body muscle mass. Controversy remains regarding applicability of psoas muscle to identify patients at greater risk of mortality. We aimed to determine psoas muscle index (PMI) association with skeletal muscle index (SMI) and to evaluate the capacity of PMI to predict liver transplant waitlist mortality. We evaluated listed adult patients with cirrhosis from 2012 to 2013 at four North American liver transplant centres. From L3 computed tomography images within 3 months of listing, we determined SMI and PMI expressed by cm2 /m2 . Low SMI was defined as SMI <39 cm2 /m2 in women and <50 cm2 /m2 in men as published by us earlier. Cut-offs for PMI to predict mortality were established using a receiver-operating characteristic analysis. Mortality predictors were determined using competing-risk analysis with reported results as subdistribution hazard ratios (sHRs). Of 353 waitlist candidates, 68% were men, mean age 56 ± 9 years, and Model for End-stage Liver Disease of 16 ± 8 points. Low SMI was present more frequently in men than women (51 vs. 36%, P = 0.02). Moderately strong correlation between SMI and PMI was observed (r > 0.7, P < 0.001). Low PMI (males < 5.1 cm2 /m2 ; females < 4.3 cm2 /m2 ) yielded poor and moderate concordance with low SMI in men and women, respectively (Kappa coefficient 0.31 and 0.63). SMI (39 ± 9 vs. 43 ± 7 cm2 /m2 ; P = 0.009) and PMI (4.4 ± 1.3 vs. 5.2 ± 1.1 cm2 /m2 ; P = 0.001) were lower in women who died and/or were delisted (compared with non-deceased patients) whereas men who died and/or were delisted had only lower SMI (47 ± 7 vs. 51 ± 9 cm2 /m2 ; P = 0.003), but not PMI compared with non-deceased patients. In women, both SMI (sHR 0.94, P = 0.048) and PMI (sHR 0.58, P = 0.002) were predictors of mortality, while in men, SMI was significant (sHR 0.95, P = 0.001) and PMI showed a trend to be (sHR 0.85, P = 0.09) associated with mortality. Overall, 104 patients (29%) were misclassified between SMI and PMI categories. Using PMI cut-offs, 66% and 28% of low SMI men and women, who have a higher risk of mortality, were incorrectly classified as low risk. Skeletal muscle index is a more complete and robust measurement than PMI, especially in men with cirrhosis. Low PMI identifies an incomplete subset of patients at increased risk of mortality indicated by low SMI. Given the poor performance of PMI, SMI should not be substituted by PMI.

Ebadi M ，Wang CW ，Lai JC ，Dasarathy S ，Kappus MR ，Dunn MA ，Carey EJ ，Montano-Loza AJ ，From the Fitness, Life Enhancement, and Exercise in Liver Transplantation (FLEXIT) Consortium ... -  《-》

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》