Inter-rater Agreement for the Clinical Dysphagia Scale

OBJECTIVE: To investigate the inter-rater agreement for the clinical dysphagia scale (CDS). METHOD: Sixty-seven subjects scheduled to participate in a video-fluoroscopic swallowing study (VFSS) were pre-examined by two raters independently within a 24-hour interval. Each item and the total score were compared between the raters. In addition, we investigated whether subtraction of items showing low agreement or modification of rating methods could enhance inter-rater agreement without significant compromise of validity. RESULTS: Inter-rater agreement was excellent for the total score (intraclass correlation coefficient (ICC): 0.886). Four items (lip sealing, chewing and mastication, laryngeal elevation, and reflex coughing) did not show excellent agreement (ICC: 0.696, 0.377, 0.446, and κ: 0.723, respectively). However, subtraction of each item either compromised validity, or did not improve agreement. When redefining 'history of aspiration' and 'lesion location' items, the inter-rater agreement (ICC: 0.912, 0.888, respectively) and correlation with new videofluoroscopic dysphagia score (PCC: 0.576, 0.577, respectively) were enhanced. The CDS showed better agreement and validity in stroke patients compared to non-stroke patients (ICC: 0.917 vs 0.835, PCC: 0.663 vs 0.414). CONCLUSION: The clinical dysphagia scale is a reliable bedside swallowing test. We can improve inter-rater agreement and validity by refining the 'history of aspiration' and 'lesion location' item.