Objectives: An empirical, head-to-head comparison of the performance characteristics of four generic health status measures.
Methods: The Nottingham Health Profile, the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36), the COOP/WONCA charts, and the EuroQol instrument were simultaneously employed in a controlled survey measuring the impact of migraine on health status. The feasibility (number of missing cases per item), internal consistency (Cronbach's alpha), construct validity (correlation patterns and common factor analysis), and discriminative ability (Receiver Operating Characteristics analyses) of the four measures were investigated.
Results: The Nottingham Health Profile produced the lowest missing value rate. The internal consistency of the Nottingham Health Profile scales was lower than the scales of the SF-36. Combined factor analyses with data of the four instruments together resulted in two-factor solutions with a physical and a mental factor, explaining approximately 50% of variance. The SF-36 exhibited the best ability to discriminate between groups. Test-retest reliability and sensitivity to change over time could not be tested because of the cross-sectional character of the study.
Conclusions: None of the instruments performed uniformly as "best" or "worst." Purely on the basis of the results of the psychometric analyses, the SF-36 appeared to be the most suitable measure of health status in this relatively healthy population. In general, the choice of the most suitable instrument for generic health status assessment in a particular study should be guided by the special features of each candidate instrument under consideration.