Are We Missing the Opportunity to Measure Muscle Mass on Computed Tomography Thorax?

Hand grip strength (HGS) and fat free mass index (FFMI) are important indicators of skeletal muscle mass and correlate with prognosis in patients with respiratory diseases. It is also possible to estimate muscle mass by measuring muscle density and volume on cross sectional imaging. We reviewed all patients of the All Wales Cystic Fibrosis Centre who had a computed tomography thorax as part of routine clinical care between 2013 and 2017. By multiplying the volume and average Hounsfield units of the paraspinal muscles at T4 and T12 levels we were able to estimate the patients skeletal muscle mass. This was compared with their FFMI, HGS and forced expiratory volume in 1 second. Measurements of muscle mass at T4 and T12 showed significant correlation with HGS and FFMI, and T12 also showed significant correlation with forced expiratory volume in 1 second. This method may provide further prognostic information for patient with cystic fibrosis, particularly where equipment for HGS and FFMI assessments are lacking.