Quantifying Pharyngeal Residue during Videofluoroscopic Swallow Studies (VFSS/MBS): Validation of Percentage-Based...

Introduction: Computerized, percentage-based assessments of pharyngeal residue (e.g., % filling of the valleculae) during videofluoroscopic swallow studies (VFSSs) offer a high level of precision, validity, and reliability compared to more frequently used visual-perceptual categorical-based rating methods (e.g., mild, moderate, severe). Despite these advantages, clinical practice largely relies on visual-perceptual methods, given their ease, speed, and lack of need for specialized software or training. Percentage-based visual-perceptual residue ratings could represent a scalable and clinically feasible alternative to computerized techniques; however, their accuracy and reliability have not been systematically investigated. Therefore, this study aimed to: evaluate the accuracy of visual-perceptual percentage-based ratings of pharyngeal residue during VFSS compared to pixel-based ground-truth measurements; characterize the inter- and intra-rater reliability of these ratings; and explore whether clinician characteristics are associated with rating accuracy.

An anonymous international survey was distributed to speech-language pathologists (SLPs). Respondents were asked to provide visual-perceptual ratings of pharyngeal residue for 40 pairs of unique fluoroscopic images. Digital tracings were superimposed onto each image to guide percentage-based ratings. SLP respondents provided two types of residue ratings: Bolus Clearance Ratio (BCR; n = 20) and Residue Ratio Scale for the valleculae (RRS_V; n = 20). 50% of the images were randomly repeated to assess intra-rater reliability. Ratings were compared to ground-truth values. Statistical analyses were used to characterize rater accuracy and reliability.

129 SLP respondents participated in the survey, yielding an analysis of 6,569 visual-perceptual percentage-based residue ratings. Residue ratings showed moderate-to-substantial agreement with ground-truth values for both BCR (ρ_c = 0.92) and RRS_V (ρ_c = 0.94). Group-level inter-rater reliability was good-to-excellent for BCR (ICC = 0.90) and excellent for RRS_V (ICC = 0.93). Intra-rater reliability was also excellent (BCR ICC = 0.92; RRS_V ICC = 0.97). Greater accuracy was associated with clinicians with fewer years of clinical experience (r = 0.35, p = 0.006), clinicians who used frame-by-frame analysis more frequently in their clinical practice (τ = 0.228, p = 0.002), and clinicians who used standardized residue rating tools such as DIGEST and MBSImP more frequently in their clinical practice.

Visual-perceptual percentage-based residue ratings during VFSS demonstrate a high level of accuracy and inter- and intra-rater reliability. Clinician experience and practice patterns influence rating accuracy. These findings support the potential clinical utility of percentage-based visual-perceptual methods as a valid and accessible alternative to traditional ordinal residue scales.