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Does adding MS-specific items to a generic measure (the SF-36) improve measurement?
J A Freeman1, J C Hobart, A J Thompson
1Institute of Neurology, Queen Square, London, United Kingdom.
Neurology
|July 11, 2001
Summary
Adding items to the Short Form Health Survey Questionnaire (SF-36) to create the Multiple Sclerosis Quality of Life Scale (MSQOL-54) did not significantly improve measurement properties. New scales showed limited validity and responsiveness, questioning the benefit of simple item addition for disease-specific measures.
Area of Science:
- Health Outcomes Research
- Psychometrics
- Rehabilitation Medicine
Background:
- The Short Form Health Survey Questionnaire (SF-36) is a standard generic health measure.
- The Multiple Sclerosis Quality of Life Scale (MSQOL-54) was developed by adapting the SF-36 with additional items for multiple sclerosis (MS).
Purpose of the Study:
- To compare the measurement properties of the MSQOL-54 with the original SF-36.
- To evaluate the impact of added items on the psychometric performance of the MSQOL-54.
Main Methods:
- 150 patients with MS completed the MSQOL-54 and other questionnaires.
- Psychometric methods were used to assess validity and responsiveness.
- 44 patients completed measures pre- and post-inpatient rehabilitation.
Main Results:
- Measurement properties of unchanged and altered SF-36 scales within MSQOL-54 remained largely identical.
- New scales demonstrated questionable validity (sexual scales) and limited validity/responsiveness (overall quality-of-life scale).
- High missing data affected the validity of sexual health scales.
Conclusions:
- Simply adding clinically selected items to existing instruments may not enhance their measurement properties as expected.
- The development of disease-specific measures requires more than just appending new items to generic tools.