Toronto Rehabilitation Institute, Toronto, ON, M5G 2A2, Canada.
In this study we explored the validity of clinician judgments of voice abnormalities as indicators of penetration-aspiration or other swallowing abnormalities. Voice samples were collected using a high-quality microphone from 40 adults during videofluoroscopy (VFSS), at baseline and following each of four thin liquid swallows. Blinded speech-language pathologists (SLPs) rated the audio recordings for voice quality using the GRBAS scale and the VFSS recordings for abnormal swallow onset, penetration-aspiration, airway closure, and pharyngeal residues. Acoustic measures of % jitter, % shimmer, and signal-to-noise ratio were calculated using two /a/ vowel segments spliced from each voice recording. Preswallow to postswallow measures of voice-quality change were derived and the data were compared to determine the correspondence between perceived voice abnormalities, acoustic voice parameters, and radiographically confirmed swallowing abnormalities. The sensitivity of perceived postswallow changes in voice quality to dysphagia and penetration-aspiration was poor, ranging from 8 to 29%. Specificity was stronger for both penetration-aspiration (75-94%) and dysphagia (59-86%). Acoustic measures of voice quality had moderate sensitivity and specificity for both dysphagia and penetration-aspiration. Overall, perceptual judgments of postswallow wet voice showed the strongest potential for detecting penetration-aspiration (relative risk = 3.24). We conclude that a clear postswallow voice quality provides reasonable evidence that penetration-aspiration and dysphagia are absent. However, observations of abnormal postswallow voice quality can be misleading and are not a valid indication that penetration-aspiration or dysphagia exists.