Validity and Reliability of Ultrasound Assessment of Swallowing Function: A Systematic Review and Meta-Analysis

The use of ultrasound (US) makes it convenient to identify dysphagia or swallowing impairment. The aim of the study was to evaluate the validity and reliability of US measurements for swallowing function.

We conducted a systematic review and meta-analysis. Embase, Medline, Cochrane Library, Web of Science, CINAHL, and Scopus databases were systematically searched from inception to July 22, 2024. Published studies on the validity and reliability of US measurements for assessing dysphagia or swallowing impairment in individuals aged 18 years and older were included. The review followed PRISMA guidelines and was evaluated using the QUADAS-2 tool for diagnostic studies. Two authors independently screened potentially eligible literature, evaluated the quality of the included studies, and then extracted the data. Data synthesis was conducted via random-effects meta-analysis using Stata software.

This review included 38 articles, assessing the value of using hyoid bone displacement, thyrohyoid approximation, and tongue muscle thickness change on US for identifying dysphagia. The pooled sensitivities were 0.64 (95% CI: 0.50-0.79), 0.89 (95% CI: 0.66-1.11), and 0.60 (95% CI: 0.44-0.76), respectively; with pooled specificities of 0.71 (95% CI: 0.64-0.78), 0.82 (95% CI: 0.76-0.88), and 0.69 (95% CI: 0.62-0.77), respectively. Additionally, the area under the summary receiver operating characteristic curve (SROC) for identifying dysphagia using masseter thickness was 0.74 (95% CI: 0.70-0.78). The correlation coefficient of 0.58 (95% CI: 0.20-0.81) was observed between displacement and swallowing function, whereas the correlation for swallowing muscle cross-sectional area (CSA) was 0.26 (95% CI: 0.09-0.42). Meta-analyses revealed intrarater reliability values of 0.88 (95% CI: 0.76-0.94) for displacement, 0.93 (95% CI: 0.87-0.96) for CSA, 0.77 (95% CI: 0.73-0.80) for swallowing muscle thickness, and 0.79 (95% CI: 0.74-0.84) for echo intensity. Interrater reliability values were 0.75 (95% CI: 0.55-0.87) for displacement, 0.89 (95% CI: 0.83-0.94) for CSA, and 0.68 (95% CI: 0.57-0.75) for swallowing muscle thickness.

Data from this review suggested that US was a reliable and valid screening tool for assessing dysphagia and swallowing impairment. Future research could aim at proposing standardised and universal US protocols to promote comparability and reliability in clinical practice.