Poster Presentation 6th Annual Scientific Meeting of the Australian and New Zealand Society for Sarcopenia and Frailty Research 2024

Diagnostic power of serum creatinine to cystatin C ratio for identifying low MRI-muscle volume and low grip strength: Data from 9,731 to 149,707 UK Biobank adults   (#7)

Ben Kirk 1 2 , Chia-Ling Kuo 3 , Peiran Liu 3 , Meiruo Xiang 3 , Jesse Zanker 1 , Konstantinos Prokopidis 4 , Marc Sim 5 , Richard H Fortinsky 3 , George A. Kuchel 3 , Gustavo Duque 6
  1. Department of Medicine, Melbourne Medical School, Melbourne, Victoria, Australia
  2. Australian Institute for Musculoskeletal Science (AIMSS), The University of Melbourne and Western Health, Melbourne, Victoria, Australia
  3. UConn Center on Aging, University of Connecticut, Farmington, CT, USA
  4. Department of Musculoskeletal Biology, Institute of Life Course and Medical Sciences,, University of Liverpool, Liverpool, UK
  5. Nutrition and Health Innovation Research Institute, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
  6. Bone, Muscle & Geroscience Group, Research Institute of the McGill University Health Centre, Montreal, QC, Canada

Background: Serum creatinine to cystatin C (Cr:Cyc) ratio has emerged as a promising biomarker for sarcopenia, yet the relationship between this biomarker and the gold standard measure of muscle volume is unknown. We examined the diagnostic power of Cr:Cyc for identifying low MRI-muscle volume in a large observational study of UK Biobank adults.

Methods: Serum creatinine and cystatin C were measured via immunoassays (Beckman Coulter AU5800 and Siemens Advia 1800, respectively); total thigh fat-free muscle volume (FFMV) by MRI; DXA-derived appendicular lean mass; and grip strength by hydraulic hand dynamometer. Extreme outliers were removed, and potential covariates (demographic, lifestyle and clinical factors) were considered in statistical models.

Results: 12,873 older adults (mean age: 63.5 ± 2.7 years, 44.2% women) were included for FFMV and ALM/BMI; 149,707 older adults (mean age: 64.0 ± 2.9 years, 50.5% women) for grip strength. Despite significant associations (p<0.05), in fully-adjusted models, Cr:Cyc showed poor to acceptable diagnostic power for identifying low FFMV when using cutpoints of 20th percentile (AUC: 0.577 men; 0.622 women) and T scores of -2 (AUC: 0.596 men; 0.659 women) and -2.5 (AUC: 0.609 men; 0.722 women). In fully-adjusted model, Cr:Cyc showed poor diagnostic power (AUCs: <0.70) for identifying low ALM/BMI or low grip strength irrespective of the cutpoint used.

Conclusions: Cr:Cyc may not be a suitable biomarker for identifying low muscle volume or strength in older adults. This finding, drawn from a large sample size and the use of advanced medical imaging, marks an important contribution to the sarcopenia field.