Rating scales
The study was conducted using a five-category scale (Table 1), to determine if subtle differences in vocal cord motion can be visualised consistently between clinicians. It goes beyond the routine practice of describing motion as normal, paresis and paralysis, which is effectively a three-category scale. Hence a three-category scale was derived from the original five category scale to know the agreement/reliability using categories (normal/paresis/paralysis) that clinicians would normally use. This would allow comparison between the three and five category scales. The recategorization from five to three category was as follows; scores assigned to categories 0 and 1 were grouped together to form the ‘immobile’ category, the scores assigned to categories 3 and 4 were grouped together to form the ‘fully mobile’ category, and category 2 remained effectively a ‘paresis’ category, resulting in the derived clinically relevant 3-category scale. Inter and intra rater agreement and reliability measures were repeated using the derived scale.