Intra- and inter-rater reliability of swallowing-related muscle assessments using ultrasound devices.

Purpose: To evaluate the inter- and intra-assessor reliability of ultrasonographic assessment of swallowing-related muscle indices in healthy young adults.

Methods: Three examiners conducted ultrasonographic evaluations on healthy young adults (n = 34, age: ≥ 20 years) examining the thickness and area of the geniohyoid muscle, anterior belly of the digastric muscle, tongue, and the mylohyoid, masseter, and depressor anguli oris muscles. To assess inter-rater reliability, each examiner evaluated each assessment item for one subject three times on the same day. Intra-rater reliability was assessed by rater No. 3 re-evaluating the participants 4-7 days after the initial measurement, using the retest method. Image analysis was conducted by a single examiner utilizing an ultrasonography measurement tool. Statistical analysis was performed using intraclass correlation coefficients (ICCs) for intra- and inter-rater reliability.

Results: The study included 34 participants (male: 17, female: 17; age: 25 ± 2 years, body mass index: 20.3 ± 1.7 kg/m²). For intra-rater reliability for thickness of the geniohyoid muscle, ICC = 0.94 [95% CI (0.89, 0.97)], and ICC = 0.90 [95% CI (0.81, 0.93)] for the area of the anterior belly of the digastric muscle. For inter-rater reliability, ICC = 0.93 [95% CI (0.88, 0.96)] and 0.86 [95% CI (0.77, 0.92)] for the thickness of the geniohyoid muscle, and area of the anterior belly of the digastric muscle, respectively.

Conclusions: The inter- and intra-assessor reliability of ultrasound assessments of swallowing-related indices in young healthy subjects was good, exhibiting particularly high accuracy for the geniohyoid muscle and the anterior belly of the digastric muscle.