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.