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Screening Utility of Lower Limb Muscle Ultrasound for Sarcopenia in COPD Patients
Jing Huang1, Fei Guo2, Li Jiang1
1Department of Respiratory and Critical Care Medicine, Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan, People's Republic of China.
Purpose:
Sarcopenia is a common but underdiagnosed extrapulmonary complication in patients with chronic obstructive pulmonary disease (COPD) and contributes to poor clinical outcomes. This study aimed to investigate the screening utility of rectus femoris cross-sectional area (RFCSA), femoral muscle thickness (FMT), and quadriceps femoris muscle thickness (QFMT) for sarcopenia in COPD patients.
Patients And Methods:
This single-center cross-sectional study enrolled 61 COPD patients. According to the sarcopenia criteria, patients were classified into sarcopenia group (n=24) and non-sarcopenia group (n=37). All participants underwent pulmonary function tests, grip strength measurement, 6-meter walk test, 5-repetition sit-to-stand test, and bioelectrical impedance analysis. QFMT, FMT, and RFCSA were measured by a single experienced sonographer using a standardized protocol. Multivariable logistic regression and receiver operating characteristic (ROC) curve analysis were performed.
Results:
The proportion of participants with sarcopenia in this COPD cohort was 39.34% (24/61). All ultrasound parameters were significantly reduced in the sarcopenia group: QFMT (2.28 cm vs 2.57 cm, p<0.001), FMT (1.30±0.21 cm vs 1.43±0.23 cm, p=0.033), and RFCSA (4.25±0.75 cm2 vs 4.72±0.75 cm2, p=0.019). Multivariable logistic regression adjusting for age, sex, BMI, and FEV1% pred confirmed QFMT as an independent factor of sarcopenia (OR=0.121, 95% CI: 0.021-0.697, p=0.018). ROC analysis revealed that QFMT had the highest AUC among single parameters (AUC=0.767, 95% CI: 0.642-0.866). At the optimal cut-off of 2.833 cm, QFMT showed a sensitivity of 100% and specificity of 43.24%. When QFMT, FMT, and RFCSA were combined, the AUC was 0.777 (95% CI: 0.652-0.874), with a sensitivity of 50% and specificity of 94.59%, representing only a marginal improvement over QFMT alone (p=0.711 by DeLong test).
Conclusion:
Lower limb muscle ultrasound parameters, particularly QFMT, are significantly reduced in COPD patients with sarcopenia. Ultrasound appears promising as a screening tool but requires validation in larger, prospective, multicenter studies.
