Computational protocol: Computed tomography diagnosed cachexia and sarcopenia in 725 oncology patients: is nutritional screening capturing hidden malnutrition?

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Protocol publication

[…] Computed tomography scans, performed routinely as part of diagnostic investigations, were used to analyse body composition at baseline. Cross‐sectional area of muscle was analysed in contrast‐enhanced CT scans at the level of the third lumbar vertebra (L3), using OsiriX software (Version 5.0) (Pixmeo, Geneva, Switzerland), as previously described., Muscle area was normalized for stature by dividing by height in metres squared and was then reported as skeletal muscle index (cm2/m2). Skeletal muscle density was assessed by computing the mean radiation attenuation of the entire muscle area at L3 in contrast enhanced CT scans, expressed in Hounsfield units. Sarcopenia is defined as appendicular skeletal muscle mass greater than 2 SD below the mean of a healthy, reference population, while myosteatosis is characterized by low radiation attenuation secondary to increased levels of intermuscular and intramuscular fat. Sarcopenia and myosteatosis were diagnosed using previously defined sex‐specific and BMI‐specific cut‐off points, devised from a cancer population. [...] Statistical analysis was performed by SPSS (version 22) for Windows (IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp.). Preliminary analyses were carried out to ensure that the assumptions of normality, linearity, or homoscedasticity were not violated. χ2 tests were used to compare categorical variables. Receiver operating characteristic curves were generated to assess the diagnostic performance of screening tools, with the area under the curve (AUC) indicating the accuracy of the tool. The Hosmer and Lemeshow's classification of AUC values was used to classify AUC scores. Multivariate Cox proportional hazards models were used to estimate covariate adjusted hazard ratios (HRs). All statistical tests were two‐sided, and exact P‐values are reported. Significance was taken at the level of P < 0.05. […]

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