Development and Validation of the PMR-Impact Scale
Polymyalgia rheumatica (PMR) is a heterogenous condition, causing pain, stiffness and disability in older adults. It can be challenging to diagnose and manage and patients report feeling that their condition is poorly understood by healthcare professionals. Measuring the impact of PMR and its treatment from the patient’s perspective is important, yet there are no validated outcome measures to support patient and clinician decision-making.
We have developed a patient-reported outcome measure (PROM) to assess PMR-related quality of life. The development process involved qualitative interviews, iterative item development and application of classical and modern measurement theory methods. The construct validity, test-retest reliability and responsiveness of the resultant PROM, the polymyalgia rheumatica-impact scale (PMR-IS), are currently being evaluated.
The qualitative study highlighted the mismatch between ‘textbook’ PMR and experiences of participants – stiffness was longer-lasting than the classical ‘morning stiffness’ and marked functional impairment and ‘weakness’ were described. The difficult balance between managing side effects of medication versus symptom control was apparent and many described mood disturbance, fear and a sense of vulnerability. A long-list of items for the PROM was developed from this data.
Field-testing involving 250 participants, allowed item reduction and formation of dimension structure. The PMR-IS has four domains – symptoms (pain, stiffness, weakness, fatigue), function (9 items), psychological impact (4 items) and steroid side effects (10 items). Scores are presented individually for each domain.
The evaluation study recruited 200 people from primary and secondary care. Participants completed the PMR-IS, the modified Health Assessment Questionnaire (mHAQ) and the Short Form-36 (SF-36) at baseline and then the PMR-IS, the mHAQ and a series of anchor questions 2-6 weeks later. Data analysis is underway.
Why it matters:
A PROM to measure PMR-related quality of life will enable the assessment of what truly matters to people with PMR to be incorporated into research into the condition and ultimately improve person-centred care for PMR.
Helen Twohig, Wellcome Trust Doctoral Fellow, School of Primary, Community and Social Care, Keele University
Caroline Mitchell, University of Sheffield, firstname.lastname@example.org
Christian Mallen, Keele University, email@example.com
Sara Muller, Keele University, firstname.lastname@example.org