Body composition determined with computed tomography at ICU admission as a potential long-term outcome assessment tool in critically ill patients: a post-hoc analysis of a prospective, observational study

Background: Body composition evaluated with computed tomography scan (CT) at intensive care unit (ICU) admission is a predictor of short-term mortality (six months). Little is known regarding long-term outcome. Our objective was to evaluate the potential predictor role of body composition at ICU admission evaluated with CT scan and long-term mortality (two years). Methods: Post-hoc analysis of a prospective observational study. Body composition evaluated at the level of the third lumbar vertebra (L3) was analyzed with dedicated software that automatically calculated the areas (cm2), determined the tissue composition by a Hounsfield unit (HU) and extracted fat component; all parameters were normalized to patient's height. Cox regression analysis was adopted to evaluate the association between statistically significant muscle parameters at univariate descriptive analysis and 2-years survival. Results: A total of fifty-one patients were evaluated for the analysis. Those who were alive at follow-up had a higher total muscle area compared to those who did not survive, 84.7 (68-99.4) versus 65.4 (59.2-84) cm2 per meter of height (P=0.025). However, no significant difference in fat area was found between survivors and non-survivors' group: the former had a fat area of 16.3 (10.9-23.4) cm2/m and the latter had 25.2 (14.8-31.5) cm2/m (P=0.166). Total muscle area was significantly associated with two-year mortality, showing a hazard ratio of 1.03 (1.01-1.06, P=0.023). Conclusions: Total muscle but not fat area evaluated at L3 at ICU admission is a prognostic marker of mortality at long-term follow-up in critically ill patients.