Quantitative assessment of response shift in QOL research

Two assumptions which characterize the measurements of quality life (QOL) s tudies, are questioned by the present report: First, the assumption that QO L is the same thing for all subjects, is usually related to health problems and can easily be measured across subjects. Second, when this assumption i s given up by introducing subjective base-rates in an intra-subject (before -after) design, researchers still tend to assume that no response shifts oc cur on the QOL scales, e.g., that these scales maintain the same meaning an d values for subjects over time and interventions. In our study we found th at QOL had different subjective interpretations [1--4]. While for some cert ain issues in their family-life determined their quality of life, for other s these were issues at their workplace or of their health conditions. Secon d, when QOL was tested against a subjective base-line (for each individual according to their choices of domains), about eleven percent of the hyperte nsives and normotensives showed a clear response shift of scale-calibration over the period of one year. When the scores of these subjects were exclud ed, the significance of certain previously reported results changed. For ex ample, the significant difference between normotensives and hypertensives c oncerning the change in their subjective evaluation of QOL over the year an d their initial depression became more significant, while similar changes i n their evaluation of sexual impairment and control at their work-place bec ame insignificant. These results suggest that response shifts have to be tr aced and quantified, before one can claim any results (or lack of results) in 'before-after' designs, concerning subjective meaningful issues like qua lity of life.