Response shift in the perception of health for utility evaluation: an explorative investigation
Introduction
In evaluating patient utilities under cancer treatment, a patient's state of health within the periods of treatment or follow-up is often assumed to be stable at least until recurrence. This assumption is the basis for cross-sectional comparisons of different interventions. Regarding health-related quality of life (QL), however, there is increasing evidence that patients with a chronic disease may change the internal standards on which they base their QL estimation in the process of becoming and remaining ill. This phenomenon has been described as ‘response shift’ 1, 2.
We previously showed that patients with newly diagnosed colon cancer changed their internal standards of QL 1, 3. This observation was made with regard to radical resection with perioperative chemotherapy and to randomly assigned post-operative adjuvant chemotherapy or observation within a clinical trial of the Swiss Group for Clinical Cancer Research (SAKK 40/93). We described these changes as ‘reframing’, as used for similar phenomena in psychology. ‘Reframing’ signifies that patients do not assess their health against a fixed reference point (i.e. a ‘true’ baseline) but against a frame of reference which shifts in the light of experience.
Whether this phenomenon similarly affects patient-estimated health status is not known. This question is relevant for cost-utility evaluations in oncology. As an alternative to formal utility assessment, health status has been assessed in many studies by visual analogue scales, rated either by the patients or by clinicians [4]. In both cases, it is assumed that these estimates reflect a ‘true’ value for a given health status which may be compared among different populations and clinical situations. This amounts to an assumption of stable internal reference points which allow an assessment of health status at any given point in time.
Such a visual analogue scale was included in the trial cited above. It was developed for serial assessment of health status for utility evaluation in cancer clinical trials [5]. Patients were asked to imagine they would have to live the rest of their life in their current condition and to indicate how they would rate a life in this condition between perfect health and worst health.
In this report, we explore the question of whether health status estimates by patients are similarly affected by a response shift as has been shown for QL indicators, and whether this effect changes the interpretation of health status estimates.
Section snippets
The trial
The trial (SAKK 40/93) was open for all patients with radically-resected and histologically-proven adenocarcinoma of the colon with pathologically confirmed stages pT1-4 pN>0 M0 and pT3-4 pN0 M0. The patients had to have a potentially curative resection (R0-resection) and no additional rectal carcinoma. The perioperative intraportal chemotherapy was a 7-day infusion of 5-fluorouracil (5-FU) starting immediately after surgery and interrupted by a 2-h infusion of Mitomycin-C after the first 24 h.
Sample description
As described in the original report [3], 215 patients were randomised in German speaking centres. For this investigation, 187 patients with at least one pair of corresponding questionnaires for either pre/then-test comparison were selected (87%). At the time of surgery, the main reasons for missing QL data were administrative problems at the local centres. In the adjuvant phase, QL data were mainly missing due to patients' failure to send back the questionnaire.
Biomedical and sociodemographic
Discussion
In this report, we explored the question of response shift in perception of health for utility evaluation and contrasted the findings with those of physical well-being and global QL, which were previously described [3].
Baseline correlations among the three indicators were moderate, related to the fact that QL and subjective health are different although overlapping constructs. However, we found similar effects of reframing. After surgery, patients' retrospective estimates of their pre-surgery
Acknowledgements
To study reframing of QL and health perception within a clinical trial needed considerable persuasiveness and logistic efforts. We would like to thank the patients who took the time to complete the questionnaires, the data managers, nurses and surgeons who took care of this study in the centres, Heidi Gusset for central data management, and Brigitte van Wegberg for trial coordination at the beginning.
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