Measuring quality of life in patients with stable coronary artery disease after coronary revascularization Advanced analytical methods for measuring changes in HRQoL

Health-Related Quality of Life (HRQoL) is a multidimensional concept that includes physical, social, and mental functioning, and general health perceptions. Measurements of HRQoL play an important role in healthcare, not only to study the effectiveness of treatments, but also to justify policy decisions, such as allocation of resources. However, despite apparent changes in health, patients may report stable HRQoL scores over time. This contradictory finding was the key problem of this thesis and two possible causes were examined: limitations of standard questionnaires using retrospective questions and the possible influence of response shift, where changes in the meaning of self-reported HRQoL may result in an underestimation of the magnitude of change in HRQoL. In addressing these two causes, we aimed to enhance the sensitivity and comprehensiveness of HRQoL measurements. A total of 320 patients with coronary artery disease with multiple comorbidities who were scheduled for coronary revascularization completed HRQoL questionnaires one week prior to revascularization (baseline), and two weeks, three months and six months thereafter (follow-up). Results indicated that the use of retrospective questionnaires could partially explain the stability in HRQoL scores, as they are limited in detecting changes in HRQoL compared to momentary questions of HRQoL. Adding momentary measures of HRQoL provides a more accurate and comprehensive picture of changes in HRQoL. Response shift analysis provided a comprehensive insight into the different types of change in HRQoL, however it did not affect the assessment of change over time and therefore could not explain the stability in HRQoL scores.