Nutrition Biomarkers and Clinical Outcomes in Critically Ill Children: A Critical Appraisal of the Literature

Background & Aims: Malnutrition can significantly affect clinical outcomes in critically ill children. In view of the limitations of anthropometry, nutrition-related serum biomarkers have been used to assess the degree of malnutrition in the pediatric intensive care unit. The aim of this review is to critically appraise the use of nutrition-related serum biomarkers in predicting clinical outcomes in critically ill children.

Methods: We searched major databases (MEDLINE, EMBASE, CINAHL, Cochrane Library) using MeSH terms and key words related to "biomarkers", "nutrition" and "critically ill children". All studies that explored the relationship between any nutrition-related serum biomarker and clinical outcomes in critically ill children (1 day-18 years) were included. The clinical outcomes of interest were duration of intensive care unit or hospital stay, duration of mechanical ventilation and mortality.

Results: We found one randomized controlled trial and 15 observational studies involving 2068 children. In these 16 studies, 16 different nutritional biomarkers and two nutrition indices were examined. Albumin (n = 7), magnesium (n = 4), transferrin, prealbumin and calcium (n = 3 respectively) were the most commonly studied biomarkers. Seven biomarkers (25-hydroxyvitamin D, albumin, calcium, magnesium, total protein, transferrin, triglycerides) and two indices (modified nutritional index and Onodera's prognostic nutritional index) had positive associations with clinical outcomes. However, no biomarkers or nutrition indices consistently predicted clinical outcomes.

Conclusions: Current medical literature does not provide convincing data to demonstrate any association between nutrition-related serum biomarkers and clinical outcomes in critically ill children. Further research is required to identify novel and clinically robust nutrition-related biomarkers.