Ultrasonography is frequently used to measure the rectus femoris muscle cross-section area, and has been suggested to associate with poor health condition. However, no validation studies have been performed to compare rectus femoris muscle ultrasonography (RFMS) with anatomical planimetry when measuring the muscle cross-sectional area (CSA). This validation study compared the two methods of CSA measurement of unfixed (frozen) and fixed (unfrozen) rectus femoris muscle specimens obtained from elderly human cadavers. Agreement between tests was studied by Bland–Altman analysis. We found a significant difference between planimetry and RFMS of unfixed (frozen) muscle specimens (mean difference, -0.389 cm2; 95% CI, -0.144 to -0.634), p = 0.022. No significant difference was observed between the two methods when measuring fixed (unfrozen) muscle specimens (mean difference, 0.032 cm2, 95% CI, -0.007 to -0.070), p = 0.107. In fixed specimens, the 95% limit of agreement between the two methods ranged between 0.12 cm2 and -0.06 cm2 (<10% deviation); while in unfixed muscle specimens, the range was between 0.28 cm2 and -1.06 cm2 (~50% deviation). In light of the similar results obtained in fixed specimens, ultrasound is a safe and accurate method of rectus femoris muscle size assessment. In clinical practice, RFMS may be used to detect a decrease in rectus femoris muscle mass, typically associated with malnutrition of the elderly, and may therefore be a simple and practical tool for the screening of malnutrition.
Nutritional modulation as part of the integrated management of chronic obstructive pulmonary disease
