The importance of rating scale design in the measurement of patient-reported outcomes using questionnaires or item banks

Abstract

PURPOSE. To investigate the effect of rating scale designs (question formats and response categories) on item difficulty calibrations and assess the impact that rating scale differences have on overall vision-related activity limitation (VRAL) scores. METHODS. Sixteen existing patient-reported outcome instruments (PROs) suitable for cataract assessment, with different rating scales, were self-administered by patients on a cataract surgery waiting list. A total of 226 VRAL items from these PROs in their native rating scales were included in an item bank and calibrated using Rasch analysis. Fifteen item/content areas (e.g., reading newspapers) appearing in at least three different PROs were id..