Objective: Patients' experience of overall health is often assessed through a single-item global question. Here, we evaluated among patients with AS and population controls whether single-item questions on the constructs health, well-being and quality of life (QoL) are interchangeable.
Methods: In a mixed quantitative and qualitative approach, all subjects scored the three single-item globals on a numeric rating scale (0-10, best). Next, they indicated for each of the questions which aspects they had been considering when scoring. After forced reflection, globals were scored again. Dissimilarities in scores among constructs, between patients and controls, and before or after reflection were tested using mixed linear models. Themes identified per construct in the qualitative part were linked to the International Classification of Functioning, Disability and Health. The type of themes per construct was compared between patients and controls.
Results: Sixty-eight AS patients and 84 controls completed the questionnaire. Patients scored significantly worse on each global than controls (mean 6.1-6.3 vs 7.2-7.6, all P < 0.01). Within groups, however, no significant differences in scores on each construct, or in scores before or after forced reflection were found. Health-related themes were relevant to each construct for patients, but were less relevant for controls when considering well-being and QoL. Emotional functions were relevant to well-being in all participants. Social roles and financial situation were more frequently related to well-being and QoL in controls.
Conclusion: While patients and controls identified content-related dissimilarities between the three constructs studied, this was not reflected in different scores of the globals.