| Summary: | After evaluating problems in conceptualisation of Quality of Life outcomes and
establishing an operational definition of HRQoL, we focus the attention on the different dimensions of Response Shift and the theoretical Models to explaining it. We pay
special attention to Schwartz and Sprangers Model.
If Gamma change is present, the construct under assessment is not stable for
the patient; so it has no sense to compare scores because if an individual changes
conceptualization of QoL over the course of time, then answers to the same items by
the same individual may not be as comparable over time as originally thought. So, it
is crucial to capture Response Shift before Alpha change is evaluated.
The analytical approaches to assess Response Shift are discussed, paying special
attention to the statistical aspects. We found several shortcomings of Ahmavaara’s
Method for comparing factorial structures and we have developed some alternatives
to capture Beta and Gamma components of Response Shift.
Keywords: Health Related Quality of Life (HRQoL), Response Shift, Beta change,
Gamma change, Dual Statis method.
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