Inter-rater and intra-rater reliability of ultrasound imaging for measuring quadriceps muscle and non-contractile tissue thickness of the anterior thigh

Abstract

Objective: To determine intra-rater and inter-rater reliability of ultrasound imaging for measuring muscle and non-contractile (subcutaneous fat and perimuscular fascia) tissue thickness of the anterior thigh. Approach: Ultrasound imaging has been used for clinical research to assess the morphology and cross-sectional area of muscles and other musculoskeletal structures. Repeatability of measurements with the ultrasound imaging technique between operators and test re-test reliability are important and need to be established for specific muscles. Twenty-four healthy moderately active adults (aged 36–64 years), underwent B-mode ultrasound imaging by two investigators. The anterior thighs were scanned at a site two-thirds of the distance between the antero-superior iliac spine and the superior pole of the patella. Intraclass Correlation Coefficients (ICCs, model 3, 1 for inter-rater and 3, 2 for intra-rater reliability between-days) with 95% confidence intervals (CI) was used to assess reliability. Main results: Inter-rater reliability of ultrasound imaging measurements were ICC3, 1 of 0.98 (95% CI: 0.95–0.99) for muscle thickness, 0.81 (95% CI: 0.60–0.91) for subcutaneous fat, 0.78 (95% CI: 0.56–0.90) for non-contractile tissue (subcutaneous fat combined with perimuscular fascia), and 0.70 (95% CI: 0.42–0.86) for perimuscular fascia. Intra-rater reliability values were ICC3, 2 0.96 (95% CI: 0.90–0.98) for muscle thickness, 0.99 (95% CI: 0.97–0.99) for subcutaneous fat, 0.98 (95% CI: 0.96–0.99) for non-contractile tissue, and −0.02 (95% CI: −0.41–0.38) for perimuscular fascia. Significance: The present findings indicate very high inter-rater and intra-rater reliability of ultrasound imaging thickness measurements of the quadriceps muscles and non-contractile tissue of the anterior thigh, while perimuscular fascia measurements alone were not reliable between days.