Introduction: Sarcopenia and malnutrition are common among older adults, both characterized by the presence of low muscle mass. Early detection is essential to prevent adverse outcomes. Although international guidelines support the use of calf circumference (CC) as an alternative to gold-standard methods (e.g., dual-energy X-ray absorptiometry [DEXA]), supporting evidence remains limited. Moreover, CC values may be affected by clinical factors such as hypoalbuminemia, which alters oncotic pressure and may cause edema, potentially leading to false-negative results. This study examined the agreement between CC and DEXA in diagnosing sarcopenia and malnutrition, and assessed the moderating effect of albumin on CC.

Methods: Data from 1,048 older adult (>65) participants in Wave 2 of the National Health and Nutrition Examination Survey (NHANES) were analyzed. Appendicular skeletal muscle mass (ASM) was estimated using both CC and DEXA. Sarcopenia was defined by low muscle mass and reduced walking speed. Malnutrition was identified using GLIM criteria. Urinary albumin was measured via fluorescent immunoassay. Pearson’s correlation, Kappa analysis, and adjusted linear regression were used.

Results: CC (r = 0.592) and the ASM derived from CC (r = 0.592) showed a moderate correlation with DEXA-based ASM. This correlation weakened (r = 0.355) when values were adjusted for height² (skeletal muscle index). Regression analysis showed that each one-unit decrease in urinary albumin was associated with a 0.437 cm increase in CC. Kappa analysis showed moderate agreement for malnutrition (κ = 0.635) and poor agreement for sarcopenia (κ = 0.372) when comparing CC-based and DEXA-based assessments.

Conclusion: CC may not be a valid proxy for muscle mass in older adults, especially in the presence of hypoalbuminemia. Assessments based on CC and DEXA may classify different individuals as sarcopenic or malnourished.