Response shift

It is useful to address what is actually being measured when discussing changes in QL. As discussed above, Calman [5] defined QL as the difference between expectations and current experience. Thus a small gap between expectations and experience would relate to good QL, and a large gap to poor QL. To improve QL one needs to reduce the gap. However, there are two ways of doing this. Current experience can be improved, by giving a therapy to improve how a person is feeling, or alternatively expectation can be reduced. This does not necessarily mean denying hope but making expectations more realistic. For instance, with increasing age come changes in priorities and goals and although physical activity may decrease, social, emotional and intellectual aspects may improve. Thus, if expectations regarding physical activity are reduced, overall QL may improve even with declining physical health.

Such changes in patients' expectations (in effect, changes in patients' internal standards) may explain the remarkable finding that many studies show that cancer patients do not report themselves to be more anxious, depressed or unhappy than the non-cancer general population. Indeed, Cassileth etal. [20] found that the mean score on the Mental Health Index of the General Well-being Scale for melanoma patients was actually slightly better than for the general public. Another study by the same group [21] noted that patients who had been living with their illness had better mental health scores than those newly diagnosed and explained this as an adaptation or adjustment to their illness. Such findings may be at odds with the external view of doctors, nurses and patients' friends and families.

Changes in patients' internal standards are not solely related to cancer. An extraordinary study by Brickman et al. [22] compared the happiness levels of paralysed victims of road accidents with lottery winners. Although differences were observed the authors state that the accident victims did not appear nearly as unhappy as might have been thought. This adds to previous literature suggesting that poorer, blind or disabled people are not unhappier than the general population [23-27].

Patients who report fewer symptoms or better QL than perhaps might have been expected by external observers are deemed to have under-reported their QL. In cancer, under-reporting maybe due to defence mechanisms (denial), adaptation to a changed situation, or social comparison (favourably comparing oneself with others in the same situation), and this generally will result in minimizing the reported change. However, this is not always the case, as when patients improve over time, they can sometimes exaggerate the change, as looking back they consider they were in a worse state. Equally, in the study by Brickman [22], it is particularly interesting that when questioned about 'past happiness' the accident victims rated themselves as being significantly happier in the past, compared to the control group. This therefore may indicate a response shift (i.e. as a result of their accident they have changed their internalized standards).

Response shift, adaptation, and under-reporting are difficult to measure, and the main method of investigating this phenomenon has been the use of the 'thentest' [28], comparing patients' responses at the time with how they recall feeling (for example, comparing QL responses made pre-treatment with a questionnaire given out post-treatment but asking about pre-treatment QL). However, the ability of patients to recall accurately casts doubt on the validity of such methods.

Nevertheless, we have to be very aware that patients' self-reporting, although undoubtedly the best measure of QL available, may not always be as informative as it might initially appear. This is particularly true if we are trying to make statements about changes in QL over time on a particular treatment. Although we need to be aware of response shift, it is less of an issue in randomized trials where the primary comparison is across groups, and can usually be considered as additional 'noise.'

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