Towards patients' understanding of health-related quality of life-a mixed-method study in psoriasis and multiple sclerosis.

Purpose: Patients' individual understanding of health-related quality of life (HRQoL) varies widely, making the measurement of this complex and subjective construct challenging. Anchoring vignettes, i.e., descriptions of fictive patients may provide insights into patients' individual questionnaire reference frames, assessment processes, and understanding of HRQoL. This study analyzes how patients assess HRQoL of vignettes.

Methods: This exploratory mixed-method study included 100 patients with a chronic disease (50 multiple sclerosis (MS); 50 psoriasis). Sixteen vignettes, two for each domain of the SF-12v2, were developed based on literature recommendations and pretested in a convenience sample of seven healthy individuals. Patients assessed their own HRQoL and HRQoL of the vignettes on the SF-12v2. In semi-structured interviews, they justified their assessments. We quantitatively analyzed associations of vignette assessments with individual characteristics using linear regression models and qualitatively analyzed assessment justifications.

Results: Patients' age and disease were significant (p < 0.05) predictors for ten and seven vignette assessments, respectively. Older patients assessed vignettes being less extreme; patients diagnosed with MS rated them more positively. Overall, adjusted R values ranged from 0.033 to 0.172. Qualitatively, most of the ratings were based on the evaluation of symptoms or impairments in daily life. Fewer participants ranked different dimensions of HRQoL in a personal hierarchy or assumed impairments beyond the vignette description.

Conclusions: The understanding of HRQoL may vary substantially and is associated with individual characteristics, individual assessment strategies, and probably other intrinsic factors as explained variance was quite low. Therefore, usage of generic instruments only allows for limited comparison across groups.