Abdominal CT Scans that Assess Body Composition of Hospitalized COVID-19 Patients Can Predict Adverse Outcomes

Obesity is a strong risk factor for adverse outcomes in patients hospitalized with COVID-19, although the distribution of fat and the amount of muscle mass are more accurate risk factors than body mass index (BMI), according to a new study.

The objective of the study by researchers at Harvard Medical School (Boston, MA, USA) was to assess body composition measures obtained on opportunistic abdominal computed tomography (CT) as predictors of outcome in patients hospitalized with COVID-19. The researchers hypothesized that elevated visceral and intermuscular adipose tissue would be associated with adverse outcome.

Several studies suggest that obesity is a strong risk factor for adverse outcome in patients hospitalized with COVID-19. BMI is commonly used to assess obesity, but cardiometabolic risk and mortality vary considerably among patients with the same BMI, which is partially attributable to differences in body composition. The distribution of fat and the amount of muscle mass are more accurate risk factors than BMI for cardiometabolic risk. Patients admitted to the hospital for COVID-19 often undergo CT of the chest or abdomen for clinical care and these CTs could be used to assess body composition without additional costs or radiation exposure.

In the latest study, the researchers looked at 124 patients (median age: 68 years, IQR: 56, 77; 59 weeks, 65 months) who were admitted with COVID-19 to a single hospital and who had undergone abdominal CT for clinical purposes. Visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), intermuscular adipose tissue (IMAT), and paraspinal and abdominal muscle cross-sectional areas (CSA) were assessed. Clinical information including prognostic factors, time of admission to the intensive care unit (ICU) and time of death within 28 days were obtained. Multivariate time-to-event competing risk models were fitted to estimate the hazard ratio (HR) for a composite outcome of ICU admission/mortality associated with a one standard deviation increase in each body compositional measure. Each model was adjusted for age, sex, race, BMI, and cardiometabolic comorbidities.

The study found that there were 50 patients who were admitted to the ICU or deceased over a median time of 1 day [IQR 1, 6] from hospital admission. Higher VAT/SAT ratio (HR of 1.30; 95% CI 1.04-1.62, p = 0.022) and higher IMAT CSA (HR of 1.44; 95% CI 1.10-1.89, p = 0.008) were associated with a reduced time to ICU admission or death in adjusted models. The researchers concluded that VAT/SAT and IMAT are predictors of adverse outcome in patients hospitalized with COVID-19, independent of other established prognostic factors. This suggests that body composition measures may serve as novel biomarkers of outcome in patients with COVID-19.

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