Interpreting differences over time in patient self-evaluation

The survey of patients with hip and knee osteoarthritis reported by Peters et al showed improvement or no change in a substantial proportion of patients followed up by telephone after 7 years.¹ Consequently, the authors conclude that osteoarthritis does not invariably deteriorate, but such conclusions bear closer investigation. Outcome assessment involved score criteria including assessment of pain and functional activities. How though might an individual's appraisal of pain or disability reflect either ‘true’ change (physical improvement) or consideration of other factors?

Longitudinal assessment requires stability of the construct being assessed. It is possible though that responder conceptualisation of what is being assessed alters through a natural process of accommodation and coping with chronic illness. Self-evaluation of pain to which a patient has accommodated may indicate stability or even improvement, even though the underlying physical pathology is marked by deterioration.² The patient effectively re-calibrates their own internal scale for response. Change in outcome may reflect individual coping abilities. That deterioration in outcome score and consulting behaviour were strongly associated may alternatively indicate that both reflect sub-optimal coping strategies.

Restriction to customary functional activities such as walking, working or other physical activities may lead patients to focus on those aspects of their life that are still achievable and from which they can continue to derive value. In doing so, individuals may re-conceptualise their understanding of ‘functional activities’ or ‘ability to work’, and may also alter the way that they implement these activities (such as with the use of a walking stick).

These psychological processes may be considered normal adaptive strategies and allow patients to retain adequate quality of life in the face of physical deterioration. This paradoxical separation of subjective wellbeing and physical status has been observed in various clinical settings. Re-calibration and re-conceptualisation together represent a response shift in patient self-evaluation and may serve to attenuate the observed impact of disease.³ However, the underlying pathology is still present and may continue to disadvantage the patient.

The point here is one of interpretability: what does an outcome measure tell us about the patient's experience and how can it inform us about how experience changes over time? Methods to explore such change processes, including individualised approaches, are emerging to sit alongside conventional assessment.³ We heartily endorse the authors' recommendation for further research on measuring change and especially that patient assessment should be in a broad biopsychosocial model that attempts to understand the individual's unique perspective.