Understanding the patient experience of stiffness, and developing a stiffness patient-recorded outcome measure, in rheumatoid arthritis

• Main Author: Halls, S.
• Published: University of the West of England, Bristol 2016
• Subjects: 616.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.698773

Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease. Stiffness is a major symptom of RA which is commonly reported by patients, affects patients’ daily life, and is relevant to patients in relation to fluctuating aspects of RA such as flare and low disease activity. Morning stiffness is also frequently used as an outcome measure both clinically and in research. Despite the relevance and uses of stiffness, it remains poorly understood and was omitted from the RA core set because of poor measurement properties. A pragmatic, mixed methods approach was used to better understand the patient experience of stiffness in people with RA and to develop and test a new RA stiffness patient reported outcome measure (PROM). It involved a systematic literature review, semi-structured interviews, focus groups, cognitive interviews, the development of appropriate candidate items to characterise stiffness and multivariate analysis of a survey using these items. The systematic literature review found that current stiffness assessment is based on items that capture the duration or severity of morning stiffness. However, items were often poorly defined, highly variable in wording and format, had limited measurement property evidence and had not been developed according to current standards including collaboration with patients. Overall, there was no evidence regarding the most appropriate way to assess stiffness in RA, indicating the need for a new measure developed according to best practice PROM guidelines. Semi-structured interviews with RA patients provided an improved understanding of their experience of stiffness, demonstrated its relevance to patients and enabled the development of a conceptual model. These data also highlighted inconsistencies between current stiffness assessment and the patient perspective of this symptom. Focus groups with RA patients reinforced the stiffness conceptual model in a new sample, using a different method of data collection. They also provided information specifically addressing stiffness assessment from the patient perspective, including a number of concepts for measurement instrument development. These patient-driven concepts and qualitative data were tempered with measurement theory to develop a conceptually sound yet practically appropriate preliminary set of items for a new RA stiffness PROM. Preliminary items were reviewed and modified by RA patients in cognitive interviews. Following refinement, 45 candidate items (39 new items and 6 traditional stiffness items) were taken forward to a postal survey to develop and test the structure of a new RA stiffness PROM. Analysis of the survey responses involved rigorous statistical testing including a series of iterative principal component analyses (undertaken initially with two different approaches), balancing Cronbach’s alpha for internal consistency, bootstrapping for stability, and expert judgement for clinical appropriateness. The emergent structure was the Rheumatoid Arthritis Stiffness (RAST) questionnaire with 21 items in 3-components capturing ‘stiffness severity’, ‘physical impact’ and ‘psychosocial impact’. The initial qualitative work enhanced its content validity and statistical testing for appropriate relationships with other measures of disease demonstrated good construct validity. These results provide support for RAST as an appropriate tool for use in future stiffness assessment. The development of the RAST is important in recognising stiffness as a relevant patient symptom and is a significant step towards standardised stiffness assessment. Further testing in a fresh population will generate additional evidence of reliability and sensitivity to change to support its use. The RAST provides a measure for use in new investigations of disease mechanisms and response to therapy.