A systematic literature review of patient-reported outcome measures used in gout: an evaluation of their content and measurement properties

Background: Gout is a common, monosodium urate crystal-driven inflammatory arthritis. Besides its clinical manifestations, patients often also suffer from pain, physical impairment, emotional distress and work productivity loss, as a result of the disease. Patient-reported outcome measures (PROMs) are commonly used to assess these consequences of the disease. However, current instrument endorsements for measuring such outcomes in acute and chronic gout clinical settings are based on limited psychometric evidence. The objective of this systematic literature review was to identify currently available PROMs for gout, and to critically evaluate their content and psychometric properties, in order to evaluate the current status regarding PROMs for use in gout patients. Methods: Systematic literature searches were performed in the PubMed and EMBASE databases. The methodological quality of included papers was appraised using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist, and evaluation of measurement properties (reliability, responsiveness, construct validity, floor and ceiling effects) was done in accordance with published quality criteria. Item content was appraised by linking health concepts to the International Classification of Functioning Disability and Health (ICF) framework. Results: In total, 13 PROMs were identified, of which three were targeted specifically at gout patients. The majority of the PROMs were rated positively for content validity. For most instruments, limited evidence was available for construct validity and reliability. Instruments to assess pain scored well on responsiveness and floor and ceiling effects, but not much is known about their reliability in gout. Conclusions: The physical functioning subscale of the SF-36v2 (Short Form-36 item version 2) is the only PROM that had sufficient supporting evidence for all its psychometric properties. Many of the commonly used PROMs in gout are currently not yet well supported and more studies on their measurement properties are needed among both acute and chronic gout populations.