Abstract
BackgroundDEMQOL and DEMQOL-Proxy are widely used patient reported outcome measures (PROMs) of health related quality of life in people with dementia (PWD). Growing interest in routine use of PROMs in health care calls for more robust instruments that are potentially fit for reliable and valid comparisons at the micro-level (patients) and meso-level (clinics, hospitals, care homes).MethodsWe used modern psychometric methods (based on the Rasch model) to re-evaluate DEMQOL (1428 PWDs) and DEMQOL-Proxy (1022 carers) to ensure they are fit for purpose. We evaluated scale to sample targeting, ordering of item thresholds, item fit to the model, and differential item functioning (sex, age, relationship), local independence, unidimensionality and reliability on the full set of items and a smaller item set.ResultsFor both DEMQOL and DEMQOL-Proxy the smaller item set performed better than the original item set. We developed revised scores using the items from the smaller set.ConclusionsWe have improved the scoring of DEMQOL and DEMQOL-Proxy using the Rasch measurement model. Future work should focus on the problems identified with content and response options.
Highlights
DEMQOL and DEMQOL-Proxy are widely used patient reported outcome measures (PROMs) of health related quality of life in people with dementia (PWD)
DEMQOL is selfreported by the PWD and is appropriate for use in mild/ moderate dementia, DEMQOL-Proxy is proxy-reported by a family carer on behalf of the PWD and can be used at all stages of dementia
Modern psychometric methods such as those based on Item Response Theory (IRT) [6, 7] and Rasch Measurement Theory (RMT) [8, 9] provide more stringent psychometric methods than traditional methods derived from Classical Test Theory (CTT)
Summary
DEMQOL and DEMQOL-Proxy are widely used patient reported outcome measures (PROMs) of health related quality of life in people with dementia (PWD). DEMQOL and DEMQOL-Proxy [1,2,3] are well known and widely used patient reported outcome measures (PROMs) for measuring health related quality of life (HRQL) in people with dementia (PWDs). The use and application of PROMs is changing In addition to their use in randomised controlled trials (RCTs) and other evaluative studies, there is a growing interest in the use of PROMs as part of routine monitoring of the quality of health and Modern psychometric methods such as those based on Item Response Theory (IRT) [6, 7] and Rasch Measurement Theory (RMT) [8, 9] provide more stringent psychometric methods than traditional methods derived from Classical Test Theory (CTT).
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