Laboratory assessment of nutritional status in ICU patients

Malnutrition is common during critical illness and associated with worse outcomes. To identify high-risk patients and tailor management, it is important to evaluate patients' nutritional status.

Albumin, transthyretin, transferrin and retinol-binding protein (RBP) reflect the acute-phase in critical illness and are influenced to different degrees by various consequences of critical illness, including inflammation, fluid shifts and organ dysfunction. They should not be regarded as biomarkers of malnutrition. Similarly, total circulating lymphocyte count, insulin-like growth factor-1 and interleukin-6 associate with malnutrition but are not reliable laboratory biomarkers to assess nutritional status of critically ill patients.Nonlaboratory tools to evaluate nutritional status include ultrasound evaluation of skeletal muscle thickness and computed tomographic evaluation of paravertebral or limb fat to muscle ratio.Serial transthyretin, RBP and muscle imaging can be used to monitor changes in nutritional status over time.

Assessing nutritional status in critically ill patients is complex due to the influence of inflammation, fluid shifts, and organ dysfunction on traditional biomarkers. There is an urgent need for better tools to enable tailored personalized nutritional support.