Psychology and perception
Psychological factors are important components of the multidimensional experience of pain. Patients’ emotional (e.g., depression and anxiety), cognitive (e.g., self-efficacy and acceptance) and social (e.g., interactions) state can all be affected, and influence the sensation of pain.
Our aim is to advance knowledge of the pain experience in people with arthritis using both quantitative and qualitative research methods. This information is being used to guide the development of intervention trials.
Pain experience and illness beliefs
People cope with health threats by a number of means, and how they do is influenced by their beliefs and understanding about the causes, consequences and timeline of the condition. In turn, illness and treatment beliefs can influence behaviour and clinical outcomes. However, relatively few studies have examined pain and illness beliefs of people with knee osteoarthritis.
We employ an exploratory approach, utilising semi-structured interviews and questionnaires, in order to investigate how individuals experience and think about their illness. We have investigated whether existing questionnaires provide adequate coverage of the pain experience associated with osteoarthritis of the knee. Unravelling illness representations is enabling us to develop of interventions, which are based on the perceptions, beliefs, concerns and needs of people with arthritis.
Psychometric evaluation of questionnaire measures
Current pain questionnaires tend to group items into clinical useful dimensions. However, it would be useful for target identification studies, if items were grouped according to their association with mechanistically distinct aspects of the pain experience. We are exploring emerging empirical mechanistic dimensions in a questionnaire set composed of outcome measures relevant to osteoarthritis knee pain.
Psychological factors account for a moderate proportion of the variance in pain. However, this may have been underestimated if each questionnaire used contains items that are inappropriate for people with osteoarthritis. We are conducting Rasch analysis on the questionnaire set with the view to refining the measures and exploring their psychometric properties. Factor analysis is then being conducted on these refined measures to establish discrete measurement dimensions. Furthermore, multiple regression is also being performed to evaluate potential mediators and moderators between pain and quality of life using the Rasch-scaled versions of the questionnaires.
Quantitative Sensory Testing (QST) offers a method of measuring pain. Patients are presented with a stimulus (e.g., pressure) in an affected or unaffected area and asked to indicate whether they can feel it and whether it is painful. This is used to establish sensory and pain thresholds. People with osteoarthritis often present with sensitivity to painful stimulation not only on their affected joints, but also at remote sites such as the sternum (breast bone). We are evaluating QST as a predictor of osteoarthritis knee pain in conjunction with psychological variables.
Relationships between pain mechanisms and pain experience
We are using both QST and brain imaging to determine how the pain experience is related to specific pain mechanisms. For example, we have found that people who report 'neuropathic' features as measured by the painDETECT questionnaire, display evidence of pain augmentation by their central nervous system.
Our psychological research has led us to develop and select outcome measures used in clinical trials and to test psychological interventions in people with arthritis.
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