Optimizing measurement of vision-related quality of life: a computerized adaptive test for the impact of vision impairment questionnaire (IVI-CAT)
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To compare the results from a simulated computerized adaptive test (CAT) for the 28-item Impact of Vision Impairment (IVI) questionnaire and the original paper–pencil version in terms of efficiency (main outcome), defined as percentage item reduction.
Using paper–pencil IVI data from 832 participants across the spectrum of vision impairment, item calibrations of the 28-item IVI instrument and its associated 20-item vision-specific functioning (VSF) and 8-item emotional well-being (EWB) subscales were generated with Rasch analysis. Based on these calibrations, CAT simulations were conducted on 1000 cases, with ‘high’ and ‘moderate’ precision stopping rules (standard error of measurement [SEM] 0.387 and 0.521, respectively). We examined the average number of items needed to satisfy the stopping rules and the corresponding percentage item reduction, level of agreement between person measures estimated from the full IVI item bank and from the CAT simulations, and item exposure rates (IER).
For the overall IVI-CAT, 5 or 9.7 items were required, on average, to obtain moderate or high precision estimates of vision-related quality of life, corresponding to 82.1 and 65.4% item reductions compared to the paper–pencil IVI. Agreement was high between the person measures generated from the full IVI item bank and the IVI-CAT for both the high precision simulation (mean bias, − 0.004 logits; 95% LOA − 0.594 to 0.587) and moderate precision simulation (mean bias, 0.014 logits; 95% LOA − 0.828 to 0.855). The IER for the IVI-CAT in the moderate precision simulation was skewed, with six EWB items used > 40% of the time.
Compared to the paper–pencil IVI instrument, the IVI-CATs required fewer items without loss of measurement precision, making them potentially attractive outcome instruments for implementation into clinical trials, healthcare, and research. Final versions of the IVI-CATs are available.
KeywordsVision-related quality of life Vision impairment Computerized adaptive testing Item bank Impact of Vision Impairment questionnaire
EKF contributed to the conception of the work, interpretation of the data, and drafting of the manuscript; EKF and BSL conducted the data analysis, assisted with interpretation of results, and drafted sections of the paper; JK contributed to the methodology and study design and revised the manuscript critically for important intellectual content; GW revised the manuscript critically for important intellectual content; ELL contributed to the conception of the work, interpretation of the data, and revised the manuscript critically for important intellectual content. He will act as a overall guarantor of the study.
Prof. Ecosse Lamoureux was supported by an Australian National Health and Medical Research Council (NHMRC) Senior Research Fellowship (#1045280). Dr Gwyn Rees was funded by an NHMRC Career Development Fellowship (#1061801). The funding organizations had no role in the design or conduct of this research or preparation of this manuscript. The Centre for Eye Research Australia receives Operational Infrastructure Support from the Victorian Government.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (Royal Victorian Eye and Ear Hospital Human Research Ethics Committee #04/556H, #09/923H) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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