Intra‐ and Inter‐Rater Reliability of Tongue Physical Function Assessments in Children

ABSTRACT Background Tongue function is critical for essential activities such as feeding and sleep. In particular, tongue protrusion plays a key role in maintaining airway patency during sleep. However, standardised protocols for measuring tongue protrusion are lacking, and the reliability of tongue function assessments in children remains underexplored. Objectives To assess the intra‐ and inter‐rater reliability of a novel tongue protrusion measurement method using a 3D‐printed stand, alongside established tongue measurements. Methods Fifty‐six children aged 4 to 17 years underwent two successive visits with the same rater and a third visit with a different rater, each spaced 1–4 weeks apart. Tongue protrusion strength (pProt) and endurance (eProt), elevation strength (pElev) and endurance (eElev), and tongue pressure during swallowing (pSwal) were assessed using the Iowa Oral Performance Instrument (IOPI). An adjustable 3D‐printed stand was developed and used to standardise the protrusion task. Tongue mobility was assessed using the Motricité Bucco‐Linguo‐Faciale tongue subscore (MBLF‐t), and mobility restriction due to the frenulum was measured with the Tongue Range of Motion Ratio (TRMR). Reliability was analysed using intraclass correlation coefficients (ICCs). Results pProt showed good intra‐rater reliability and moderate inter‐rater reliability, while eProt demonstrated excellent intra‐rater and good inter‐rater reliability. All other outcomes exhibited at least good intra‐ and inter‐rater reliability, except for pElev, which showed slightly lower inter‐rater reliability (ICC = 0.73). Conclusion This study highlights the reliability of tongue function assessments, including a novel IOPI‐based protrusion measurement method, supporting their use in future research and clinical practice. Trial Registration ClinicalTrials.gov ID: NCT06166680