Definitions of and instruments for disease activity, remission and relapse in polymyalgia rheumatica: a systematic literature review

Objective To perform a systematic literature review on definitions and instruments used to measure remission, relapse and disease activity in polymyalgia rheumatica (PMR), to inform an OMERACT project to endorse instruments for these outcomes.Methods A search of Pubmed/MEDLINE, EMBASE, CINAHL, Cochrane and Epistemonikos was performed May 2021 and updated August 2023. Qualitative and quantitative studies published in English were included if they recruited people with isolated PMR regardless of treatment. Study selection and data extraction was performed independently by two investigators and disagreement was resolved through discussion. Data extracted encompassed definitions of disease activity, remission and relapse, and details regarding the instruments used to measure these outcomes.Results From the 5718 records, we included 26 articles on disease activity, 36 on remission and 53 on relapse; 64 studies were observational and 15 interventional, and none used qualitative methods. Some heterogeneity was found regarding definitions and instruments encompassing the domains pain, stiffness, fatigue, laboratory markers (mainly acute phase reactants), and patient and physician global assessment of disease activity. However, instruments for clinical signs were often poorly described. Whilst measurement properties of the polymyalgia rheumatica activity score (PMR-AS) have been assessed, data to support its use for measurement of remission and relapse are limited.Conclusion Remission, relapse and disease activity have been defined heterogeneously in clinical studies. Instruments to measure these disease states still need to be validated. Qualitative research is needed to better understand the concepts of remission and relapse in PMR.Review registration PROSPERO identification: CRD42021255925.