Validity of Musculoskeletal Ultrasonography for the Assessment of Muscle Mass in Older Adults: A Systematic Review and Comparative Meta‐Analysis With DXA

INTRODUCTION: Sarcopenia is a progressive skeletal muscle disorder associated with adverse clinical outcomes, including functional decline, frailty, and mortality in older adults. Although dual-energy X-ray absorptiometry (DXA) is recommended as the reference method for the assessment of muscle mass, its limited availability restricts widespread clinical implementation. Musculoskeletal ultrasonography (US) has emerged as a promising alternative due to its portability, low cost, and absence of ionizing radiation; however, its validity relative to DXA in older populations remains insufficiently synthesized. METHODS: A systematic review and meta-analysis was conducted in accordance with PRISMA 2020 and registered in PROSPERO (CRD420251168461). Six databases were searched (2015-2025) for observational studies comparing US with DXA in adults aged ≥ 60 years. Risk of bias was assessed using QUADAS-2, and US protocols were evaluated using Pretorius and Keating criteria. Random-effects meta-analyses (REML with Knapp-Hartung adjustment) were performed to pool correlation coefficients and diagnostic accuracy outcomes. RESULTS: = 97.4%). Inter-rater reliability was excellent (ICC: 0.90-0.98). Diagnostic performance was acceptable to good (AUC: 0.75-0.95), with higher specificity than sensitivity (median: 0.91 vs. 0.74), supporting ultrasound mainly as a complementary or confirmatory tool rather than a stand-alone screening method. CONCLUSION: Musculoskeletal US is a highly correlated and reproducible tool, representing a practical option for muscle assessment and a useful complementary method for clinical evaluation and longitudinal monitoring, particularly given its high specificity. However, it should not replace DXA for formal diagnosis due to methodological heterogeneity and moderate sensitivity, highlighting the need for protocol standardization and the establishment of diagnostic cut-off values to support its integration into routine geriatric practice.