Is transthyretin a good marker of nutritional status?

The assay of plasma transthyretin (TTR), also known as prealbumin, is a key step in the assessment of nutritional status. However, it remains unclear whether it really is a useful nutrition marker, and when and how to use it and interpret TTR levels and variations. Risk of malnutrition, malnutrition severity, prognosis associated with malnutrition and effectiveness of refeeding are four parameters in nutritional assessment, and need clear separation to understand the associated utility of TTR. TTR does not have the same impact and potential on each of these parameters: it can be helpful but not essential for evaluating the risk of malnutrition, and it can diagnose malnutrition and its severity in patients with no inflammation syndrome. TTR is a good marker for prognosis associated with malnutrition, and is even better for monitoring refeeding efficacy despite inflammation. Thresholds depend on the purpose for which it is used. We propose a simple algorithm to guide the interpretation of TTR levels as a helpful tool for day-to-day practice.