Abstract
PurposeAsking patients to rate health-related quality of life (HRQoL) of hypothetical individuals described in anchoring vignettes has been proposed to enhance knowledge on how patients understand and respond to HRQoL questionnaires. In this article, we describe the development of anchoring vignettes and explore their utility for measuring response shift in patients’ self-reports of HRQoL.MethodsWe conducted an explorative mixed-methods study. One hundred patients with multiple sclerosis or psoriasis participated in two interviews at intervals of 3–6 months. During both interviews, patients assessed HRQoL of 16 hypothetical individuals on the SF-12 questionnaire (two vignettes for each of the eight domains of the SF-12). In addition to these quantitative ratings, we used the think-aloud method to explore changes in patients’ verbalization of their decision processes during vignette ratings.ResultsAgreement of vignette ratings at baseline and follow-up was low (ICCs < 0.55). In addition, paired sample t-tests revealed no significant directional mean changes in vignette ratings. Thus, ratings changed non-directionally, neither confirming retest reliability nor a systematic change of assessment. Furthermore, patients’ verbalization of their decision processes did not indicate whether or not the assessment strategy of individual patients had changed.ConclusionsPatients’ ratings of anchoring vignettes fluctuate non-directionally over time. The think-aloud method appears not to be informative in exploring whether these fluctuations are due to changes in the individual decision process. Overall, vignettes might not be an appropriate approach to explore response shift, at least with regard to the specific target population and the use of the SF-12.
Highlights
In health care, we use standardized questionnaires to convert patients’ perceived state of health-related quality of life (HRQoL) into a numerical score
Changes in HRQoL are an indicator of treatment benefit and can support individual decisionmaking in clinical practice
Response shift includes three different sub-phenomena that may lead to changes in the measured HRQoL state with no actual changes having occurred: (1) a shift in the individual definition or interpretation of the HRQoL construct, (2) a shift in the values that people assign to different domains of HRQoL and (3) a shift in the internal standards of interpreting the measurement tool [6]
Summary
We use standardized questionnaires to convert patients’ perceived state of health-related quality of life (HRQoL) into a numerical score. We calculated SF-12 domain scores which were used to explore above mentioned assumptions: Paired sample t-tests investigated whether identical anchoring vignettes were rated systematically different on group level. Vignette ratings at t1 and t2 tended to differ non-directionally, confirming neither reliability nor a directional change in the ratings of anchoring vignettes for the sample and for specific subsamples These findings give some initial indications regarding questioning the appropriateness of the anchoring vignette approach for investigating response shift in longitudinal HRQoL assessment. [Vignette II], I’d say that the general health, I would attribute to good Even if he is more limited than patient A, but he is still able to work, he has family support and, mhm, generally he is a bit slower than other people considering some things, that’s normal. It was agreed that no clear and reliable criteria for equivalence or non-equivalence can be defined because there is a high degree of uncertainty as to whether the verbalizations represent underlying differences in reasoning and reference frame or not
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