CT Scan-Derived Muscle, But Not Fat, Area Independently Predicts Mortality in COVID-19

Abstract

Background: COVID-19 has demonstrated a highly variable disease course, from asymptomatic to severe illness and eventually death. Clinical parameters, as included in the 4C Mortality Score, can predict mortality accurately in COVID-19. Additionally, CT scan-derived low muscle and high adipose tissue cross-sectional areas (CSAs) have been associated with adverse outcomes in COVID-19.

Research question: Are CT scan-derived muscle and adipose tissue CSAs associated with 30-day in-hospital mortality in COVID-19, independent of 4C Mortality Score?

Study design and methods: This was a retrospective cohort analysis of patients with COVID-19 seeking treatment at the ED of two participating hospitals during the first wave of the pandemic. Skeletal muscle and adipose tissue CSAs were collected from routine chest CT-scans at admission. Pectoralis muscle CSA was demarcated manually at the fourth thoracic vertebra, and skeletal muscle and adipose tissue CSA was demarcated at the first lumbar vertebra level. Outcome measures and 4C Mortality Score items were retrieved from medical records.

Results: Data from 578 patients were analyzed (64.6% men; mean age, 67.7 ± 13.5 years; 18.2% 30-day in-hospital mortality). Patients who died within 30 days demonstrated lower pectoralis CSA (median, 32.6 [interquartile range (IQR), 24.3-38.8] vs 35.4 [IQR, 27.2-44.2]; P = .002) than survivors, whereas visceral adipose tissue CSA was higher (median, 151.1 [IQR, 93.6-219.7] vs 112.9 [IQR, 63.7-174.1]; P = .013). In multivariate analyses, low pectoralis muscle CSA remained associated with 30-day in-hospital mortality when adjusted for 4C Mortality Score (hazard ratio, 0.98; 95% CI, 0.96-1.00; P = .038).

Interpretation: CT scan-derived low pectoralis muscle CSA is associated significantly with higher 30-day in-hospital mortality in patients with COVID-19 independently of the 4C Mortality Score.

Keywords: COVID-19; CT scan; body composition; mortality; skeletal muscle.

Graphical abstract

Figure 1

A-D, Representative examples of selected CT scan slices at the fourth thoracic vertebra level (A) with demarcated pectoralis major and minor muscle (B) and at first lumbar vertebra (L1) level (C) with demarcated L1 muscle, visceral, and subcutaneous adipose tissue (D).

Figure 2

Flow chart showing available CT scan images and tissues of interest. If a selected image was of poor quality, had artefacts, or tissue of interest was not depicted fully, the specific slice or missing tissue was considered as a missing value. L1 = first lumbar vertebra; MUMC+ = Maastricht University Medical Centre+; SAT = subcutaneous adipose tissue; VAT = visceral adipose tissue.