Is a line the same as a box? Speech assessment by VAS is not superior to Likert scales in laryngeal cancer patients.

BACKGROUND The primary purpose was to assess if VAS or Likert was relatively more suitable when assessing self-ratings of voice and speech in patients treated for laryngeal cancer. An additional purpose was to investigate whether the scales differed in measuring change after treatment. MATERIAL/METHODS Using both VAS and Likert, 71 patients answered three questions at baseline and 12 months after treatment began. For test-retest analyses, additional data were used from 21 subjects. Non-parametric statistical methods suitable for comparing scales with different numbers of response alternatives were applied. RESULTS Test-retest reliability was strongest for the Likert scale. From baseline to follow-up, both scales detected significant improvements. However, for some Likert scores the associated VAS values varied across a wide range, and this was true for assessments at baseline, at follow-up, and for score changes. At baseline the inter-scale concordance showed a greater number of disordered pairs than at follow-up and on both occasions the older group produced a greater number of disordered pairs. CONCLUSIONS No support for the superiority of VAS over Likert was found. However, VAS may produce instability in response patterns. When using self-ratings of voice and speech to identify a need of further rehabilitation, Likert scales seem better suited.