METABOLIC SUPPORT: Edited by Paul E. WischmeyerNovel methods to identify and measure catabolismPage, Alexandriaa; Flower, Lukeb; Prowle, Johna,c; Puthucheary, Zudina,cAuthor Information aCritical Care and Perioperative Medicine Research Group, Adult Critical Care Unit, The Royal London Hospital, Barts Health NHS Trust bDepartment of Anaesthesia, University College London Hospitals cWilliam Harvey Research Institute, Queen Mary University of London, London, UK Correspondence to Alexandria Page, Critical Care and Perioperative Medicine Research Group, Adult Critical Care Unit, The Royal London Hospital, Barts Health NHS Trust, Whitechapel Road, London E1 1BB, UK. E-mail: [email protected] Current Opinion in Critical Care: August 2021 - Volume 27 - Issue 4 - p 361-366 doi: 10.1097/MCC.0000000000000842 Buy Metrics Abstract Purpose of review Assess current potential catabolism-biomarkers to characterize patients developing prolonged critical illness. Recent findings A raised urea-to-creatinine ratio (UCR) during critical illness is negatively associated with muscle mass with greater increases in UCR seen patients developing persistent critical illness. Similarly, sarcopenia index (a ratio of creatinine to cystatin-c concentrations) correlates well to muscle mass in intensive care populations. Elevated growth/differentiation factor-15 (GDF-15) has been inconsistently associated with muscle loss. Although GDF-15 was a poor marker of feeding tolerance, it has been associated with worse prognosis in intensive care. Summary UCR is an available and clinically applicable biomarker of catabolism. Similarly, sarcopenia index can be used to assess muscle mass and indirectly measure catabolism based on readily available biochemical measurements. The utility of novel biomarkers, such as GDF-15 is less established. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.