RELIABILITY AND VALIDITY OF A STANDARDIZED ULTRASOUND EXAMINATION PROTOCOL TO QUANTIFY VASTUS LATERALIS MUSCLE

Objective: To evaluate the reliability and validity of a standardized ultrasound examination protocol for measuring vastus lateralis muscle size. Design: Prospective cohort study. Subjects: Sixteen staff members of the university hospital of Heidelberg. Methods: Muscle thickness, cross-sectional area and subcutaneous adipose tissue thickness were measured at 3 standardized sites on the right and left vastus lateralis muscle. Ultrasound measurements were collected by 2 independent investigators on 2 different days and compared with magnetic resonance imaging measurements. Results: Intraclass correlation coefficients (ICC) for intra-and inter-rater reliability showed very good closeness of agreement for all parameters (ICC = 0.929-0.994, p < 0.001). Muscle thickness and subcutaneous adipose tissue thickness ultrasound and magnetic resonance imaging measurements revealed good to very good closeness of agreement (ICC = 0.835-0.969, p < 0.001), whereas cross-sectional area showed only average closeness of agreement (ICC = 0.727, p < 0.001). A strong predictive positive correlation for ultrasound and magnetic resonance imaging-based measurements of crosssectional area was found (R-2 = 0.793, p < 0.001). Conclusion: By standardization of an examination protocol, quantitative vastus lateralis muscle ultrasound proved to be a reliable method for assessing vastus lateralis muscle size. Furthermore, this protocol is valid for measuring muscle thickness and subcutaneous adipose tissue thickness, although there seems to be a systematic underestimation of crosssectional area depending on subcutaneous adipose tissue thickness.

Automated summary

The study found that by standardizing an examination protocol, ultrasound measurements of muscle thickness and subcutaneous adipose tissue thickness showed good reliability and validity, while the cross-sectional area had only average agreement but still showed a strong positive correlation with magnetic resonance imaging measurements.