Prognostic Value of Bioelectrical Impedance Analysis Markers in Predicting 28- Day Mortality in Chinese ICU Patients

Abstract Bioelectrical impedance analysis (BIA) provides bedside measures of skeletal muscle and fluid distribution, but the joint prognostic value of these measures in critically ill adults remains uncertain. This prospective single-centre cohort included 461 adults, using each patient's earliest eligible ICU admission. Multifrequency BIA was performed within 8 h, and binary day-28 mortality was analysed by logistic regression. Ninety-two patients (20.0%) died by day 28. In the extended APACHE II + BIA model, higher skeletal muscle index (odds ratio [OR] 0.698 per kg/m², 95% CI 0.584–0.833) and phase angle (OR 0.604 per degree, 95% CI 0.473–0.772) were associated with lower mortality, whereas higher extracellular water/total body water ratio (OR 3.169 per 0.05, 95% CI 2.074–4.841) and APACHE II (OR 3.634 per 5 points, 95% CI 2.505–5.270) were associated with higher mortality. The extended model achieved an apparent AUC of 0.900 (95% CI 0.864–0.937) and a bootstrap optimism-adjusted AUC of 0.896. These BIA measures provided complementary prognostic information in the development cohort. External validation is required before clinical use.