A NEW meta-analysis has established global reference values for skeletal muscle index (SMI) and skeletal muscle density (SMD) on abdominal CT, offering a practical tool for opportunistic sarcopenia screening. By analysing data from over 16,000 healthy adults aged 18 to 45, researchers identified mean values and clinically relevant cutoffs for these key muscle metrics, measured at the L3 vertebral level.
CT-based muscle assessment is increasingly used to identify sarcopenia, a condition marked by low muscle mass and quality, which is associated with poorer outcomes in various clinical settings. However, the absence of widely accepted reference ranges has limited its integration into routine practice. This study addresses that gap by pooling results from 14 studies across diverse populations.
The estimated global mean SMI was 54.6 cm²/m² in men and 42.4 cm²/m² in women, while mean SMD values were 47.4 Hounsfield units (HU) for men and 43.6 HU for women. To provide clinically actionable thresholds, the researchers calculated values corresponding to a T-score of -2, representing two standard deviations below the mean. The resulting cutoffs were 36.3 for SMI in men and 27.5 in women, and 36.4 HU and 28.1 HU for SMD, respectively.
Despite considerable heterogeneity among studies, the use of random-effects modelling and pooled intrastudy variance supported the robustness of these estimates. These new reference values can help clinicians identify patients at risk of sarcopenia during routine CT imaging, even when imaging was originally ordered for unrelated reasons.
By defining global cutoffs, this work enhances the utility of CT scans in risk stratification and supports the incorporation of muscle health into broader clinical assessments. The findings provide a strong foundation for more consistent and standardised sarcopenia screening, particularly in younger adult populations where early detection may have long-term health benefits.
Aleksandra Zurowska, EMJ
Reference
Ju C et al. Defining Reference Values for Skeletal Muscle Metrics on Abdominal CT Using Data From Healthy Young Adult Populations: A Systematic Review and Meta-Analysis. AJR. 2025;DOI: 10.2214/AJR.25.3278.
