Response Shift and Dentine Hypersensitivity

Objectives: Response shift refers to the changes in the meaning of self-evaluation of quality of life (QoL) as a result of changes in internal standards of measurement (recalibration), changes in relative importance of component domains of quality of life (reprioritisation) or redefinitions of QoL (reconceptualisation). Response shift can therefore undermine the comparison of QoL within individuals over time and between individuals, for example when assessing treatment effects. The aim of this research was to investigate response shift in people with dentine hypersensitivity (DH). Methods: Two studies were conducted. A quantitative study investigated recalibration and its influence on the assessment of treatment effect in 114 participants of an 8-week randomised controlled trial of mouthwashes for DH. Two approaches: the THEN TEST and a novel approach; the IDEALS were incorporated into the Dentine Hypersensitivity Experience Questionnaire (DHEQ) to assess recalibration. A qualitative study longitudinally explored response shift and its underlying psychosocial mechanisms in 20 individuals with self-reported DH. Two semi-structured interviews were conducted 6-9 months apart and Framework analysis was used to analyse the transcripts. Results: The quantitative study found recalibration in the treatment groups. The THEN TEST indicated a downward shift in participants’ internal standards of measurement whereas the IDEALS suggested a shift upwards. Individuals shifted upwards, downwards and not at all. Additionally, recalibration was similar in the treatment and placebo groups. Accounting for recalibration reduced the apparent treatment effect in all groups. In the qualitative study two main findings emerged. First, the study described adaptation to DH and its influence on the assessment of oral health related quality of life (OHQoL). Second, a modified model of response shift emerged that distinguished between the influence of adaptation and measurement error on the assessment of QoL. Conclusion: The two studies described response shift, its psychosocial determinants and influence on the assessment of treatment effects in people with DH as an example of a mild health condition. Moreover, the two studies challenged the current conceptualisation and the dominant approach to the measurement of the phenomenon. A modified model of response shift was proposed and a novel way of its assessment, the IDEALS was initially validated.