Abstract
Background
Health Related click here Quality of Life (HRQoL) is a relevant variable in the evaluation of health outcomes.Questionnaires based on Classical Test Theory typically require a large number of items to evaluate HRQoL.Computer Adaptive Testing (CAT) can be used to reduce tests length while maintaining and, in some cases, improving accuracy.This study aimed at validating a CAT based on Item Response Theory (IRT) for evaluation of generic HRQoL: the CAT-Health instrument.
Methods
Cross-sectional study of subjects aged over 18 attending Primary Care Centres for any reason.CAT-Health was administered along with the SF-12 Health Survey.Age, gender and a checklist of chronic conditions were also collected.CAT-Health was evaluated considering: 1) feasibility: completion time and test length; 2) content range coverage, Item Exposure Rate (IER) and test precision; and 3) construct validity: differences in the CAT-Health scores according to clinical variables and correlations between both questionnaires.
Results
396 subjects answered CAT-Health and SF-12, 67.2% females, mean age (SD) 48.6 (17.7) years.
36.9% did not report any chronic condition.Median completion time for CAT-Health was 81 seconds (IQ range = 59-118) and it increased with age (p < 0.001).
The median number of items administered was 8 (IQ range = 6-10).Neither ceiling nor floor effects were found for the score.None of the items in the pool had an IER of 100% and it was over 5% for 27.1% of the items.
Test Information Function (TIF) peaked between levels -1 and 0 of HRQoL.Statistically significant differences were observed in the CAT-Health scores according to the number and type of conditions.
Conclusions
Although domain-specific CATs exist for various areas of HRQoL, CAT-Health is one of the first IRT-based CATs designed to evaluate generic HRQoL and it has here proven feasible, valid and efficient, when administered to a broad sample of individuals attending primary care settings.
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