ABSTRACT
Patient-reported outcomes (PROs) are now widely used in health-related research to assess, for instance, health-related quality of life (HRQoL), often with self-administered questionnaires. Usually, HRQoL measures are based on the assumption that the meaning of concepts and measurement scales remain stable in individuals' minds over time. Historically, the term "response shift" was introduced by Howard and Dailey in 1979 in the field of educational training. Their aim was to experimentally assess the efficacy of various training interventions proposed by psychologists in college and work environments, like improving leadership and performance appraisal or reducing dogmatism. Qualitative interviews can be conducted to generate an in-depth knowledge of how a person is experiencing changes in HRQoL over time. Historically, detecting account various types of within-individual changes over time of a targeted construct using factor analysis has been proposed even before response shift (RS) was defined in health-related research.
