Prevalence of Low Muscle Mass in the Computed Tomography at the Third Lumbar Vertebra Level Depends on Chosen Cut-Off in 200 Hospitalised Patients-A Prospective Observational Trial.

Measuring skeletal muscle area (SMA) at the third lumbar vertebra level (L3) using computed tomography (CT) is increasingly popular for diagnosing low muscle mass. The aim was to describe the effect of the CT L3 cut-off choice on the prevalence of low muscle mass in medical and surgical patients. Two hundred inpatients, who underwent an abdominal CT scan for any reason, were included. Skeletal muscle area (SMA) was measured according to Hounsfield units on a single CT scan at the L3 level. First, we calculated sex-specific cut-offs, adjusted for height or BMI and set at mean or mean-2 SD in our population. Second, we applied published cut-offs, which differed in statistical calculation and adjustment for body stature and age. Statistical calculation of the cut-off led to a prevalence of approximately 50 vs. 1% when cut-offs were set at mean vs. mean-2 SD in our population. Prevalence varied between 5 and 86% when published cut-offs were applied (p < 0.001). The adjustment of the cut-off for the same body stature variable led to similar prevalence distribution patterns across age and BMI classes. The cut-off choice highly influenced prevalence of low muscle mass and prevalence distribution across age and BMI classes.

Validation of bedside ultrasound to predict lumbar muscle area in the computed tomography in 200 non-critically ill patients: The USVALID prospective study.

BACKGROUND & AIMS: Skeletal muscle area (SMA) in the computed tomography (CT) at the third lumbar vertebra (L3) level is a proxy for whole-body muscle mass but is only performed for clinical reasons. Ultrasound is a promising tool to determine muscle mass at the bedside. It is still unclear how well ultrasound and which ultrasound measuring points can predict CT L3 SMA. METHODS: This prospective observational trial included 200 non-critically ill patients, who underwent an abdominal CT scan for any clinical reason within 48 h before the ultrasound examination. Ultrasound muscle thickness was evaluated at 3 measuring points on the thigh and 2 measuring points on the upper arm with minimal compression. On the CT scan, the entire L3 SMA was measured based on Hounsfield units. Using a model selection algorithm based on the Bayesian information criterion (BIC) and clinical considerations, a linear prediction model for CT L3 SMA based on the ultrasound muscle thickness and other independent variables was fitted and assessed with cross-validation. RESULTS: 67,5% and 32,5% of the patients were from surgical and medical wards, respectively. Mean ultrasound muscle thickness values were between 2,2 and 3,6 cm on the thigh and between 1,4 and 2,8 cm on the upper arm. All ultrasound muscle thickness values were higher in men than in women (P < 0,05). CT L3 SMA was 40 cm2 higher in men than in women (P < 0,001). The final prediction model for CT L3 SMA included the following 4 independent variables: ultrasound muscle thickness at the ventral measuring point of the thigh in the short-axis plane, sex, weight, and height. It had a similar BIC (BIC of 1515) compared to larger models with 6-8 independent variables including multiple ultrasound measuring points (BIC of 1506-1519). Additional clinical considerations to choose the final model were less time consumption when measuring a single ultrasound measuring point and better anatomical overview at the short-axis plane. The final model predicted CT L3 SMA with a R2 of 0,74 (P < 0,001) and a cross-validated R2 of 0,65. CONCLUSIONS: One single ultrasound measuring point at the thigh together with sex, height and weight very well predicts CT L3 SMA across different clinical populations. Ultrasound is a safe and bedside method to measure muscle thickness longitudinally to monitor the effects of nutrition and physical therapy.

How reliably can ultrasound help determine muscle and adipose tissue thickness in clinical settings? An assessment of intra- and inter-examiner reliability in the USVALID study.

BACKGROUND/OBJECTIVES: Ultrasound is used to measure muscle and adipose tissue thickness at the bedside. This study was aimed at determining the intra- and inter-examiner reliability for marking points to measure adipose tissue and muscle thickness and assessing it in terms of the performance and evaluation of the corresponding ultrasound scans. SUBJECTS/METHODS: Intra- and inter-examiner reliability was tested in 120 patients. Limb lengths were measured to mark three and two measuring points on both the thighs and upper arms, respectively. Ultrasound scans were performed at each measuring point to evaluate muscle and adipose tissue thickness. RESULTS: Regarding the marking of the measuring points, intra- and inter-examiner reliability were high to very high, with correlation coefficients ranging from 0.74 to 0.96. In the performance and evaluation of adipose tissue thickness, all measuring points showed a high to very high reliability, with correlation coefficients ranging from 0.70 to 0.97. In the performance and evaluation of muscle thickness, the ventral measuring point on the thigh and the anterior measuring point on the upper arm showed the best reliability, with high to very high correlation coefficients ranging from 0.77 to 0.93. CONCLUSIONS: In terms of intra- and inter-examiner reliability, the ventral measuring point on the thigh and the anterior measuring point on the upper arm can be strongly recommended for ultrasound measurements of muscle and adipose tissue thickness.