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Psychometric evaluation and computerized adaptive testing simulations of age-related macular degeneration quality of
Eva K Fenwick1, Ryan E K Man1, Anna C S Tan1
1Singapore Eye Research Institute, Singapore National Eye Center, Singapore; Duke-National University of Singapore (NUS) Medical School, National University of Singapore, Singapore.
Purpose:
To optimize the psychometric properties of age-related macular degeneration (AMD) quality of life (QoL) item banks (IBs), and evaluate their performance using computerized adaptive testing (CAT) simulations.
Design:
Cross-sectional, clinical study.
Methods:
261 AMD patients answered 219 items within seven IBs: Activity Limitation (AL); Lighting (LT); Mobility (MB); Emotional (EM); Concerns (CN); AMD Management (AM); and Work (WK), referred to collectively as "MacCAT". The psychometric properties of each IB (e.g. measurement precision; item "fit"; differential item functioning (DIF)) were assessed using Rasch analysis. The mean number of items required for "high" and "moderate" measurement precision was determined using CAT simulations.
Results:
Of the 261 participants (mean age 70.5 ± 7.6 years), 69 (26.4 %), 35 (13.4 %), 80 (30.7 %) and 77 (29.5 %) had no, early, intermediate and late AMD (better eye), respectively. AL, EM, CN and AM displayed good psychometric properties overall after collapsing response categories and deleting items for misfit and/or DIF. Despite similar reengineering efforts, LT and MB had suboptimal measurement precision but were retained due to otherwise good psychometric performances. Owing to unresolvable psychometric issues, WK was not considered further. Targeting for all IBs was suboptimal. In CAT simulations on the six remaining IBs, the mean number of items required per IB ranged from 8 (AL) to 13 (MB) for moderate, and 13 (AL) to19 (MB) for high measurement precision.
Conclusions:
Six IBs demonstrated acceptable psychometric properties and potential CAT efficiency, suggesting MacCAT provides a comprehensive measurement of the QoL impact of AMD and associated treatments. Further testing in larger clinical cohorts is needed.
