Background In psoriatic arthritis (PsA) a state of minimal disease activity (MDA) or remission are the target of treatment , but due to the heterogeneity of disease manifestations, it is still an unmet need. Coates et al  have developed and validated a composite score for MDA that encompasses most disease domains. However, for disease remission there is no accepted definition, with studies “borrowing” measures from rheumatoid arthritis or using their own criteria.
Objectives The objective of this study was to analyse existing data on the definition of MDA and remission in studies on PsA.
Methods A systematic literature review was performed. Studies evaluating remission or minimal disease activity in PsA either as a primary or secondary outcome, published between 2007–2017, were identified using the terms (“psoriatic arthritis”) AND (“remission” OR “low disease state” OR “low disease activity” OR “minimal disease state” OR “minimal disease activity”). Studies assessing disease activity in general, without specifically mentioning remission or MDA were not included; reviews and case-reports were also excluded.
Results Two hundred and thirty-five publications were identified, of which 56 were included in the final analysis. The majority were observational studies (85.5%) and there were no qualitative studies identified. In total, 10843 PsA patients were analysed: 8779 in observational studies and 2064 in interventional studies; 4823 patients fulfilled the CASPAR criteria  and 6667 (31 studies) were taking a biologic drug at their inclusion. The majority of the studies assessed either MDA (65.5%) or remission (60%), but only 14 studies (25.5%) assessed both of the two outcomes. MDA or remission were mainly used as a secondary outcome (52.7% of the studies).
MDA was assessed mainly in observational studies (61.7%) and in almost all cases (88.9% of the studies) the definition used was the one proposed by Coates et al . Remission was also assessed mainly in observational studies (63.8%). The most used definition (57.6%) was based on the disease activity score (DAS28), with values less than 2.6 considered as “remission”. Articular involvement was assessed in all cases, whilst skin psoriasis, dactylitis and enthesites were rarely included in the definition of remission (15.15% each). Physician's assessment was taken into consideration in almost a third of the studies (27.3%), but the patient's assessment (pain or global evaluation) was included in more than half of the studies (69.7%). However, other patient reported outcomes were sparsely used (i.e., fatigue and morning joint stiffness were included in only one study) or not all reported (e.g, social participation, work productivity, depression).
Conclusions Whilst for MDA there is a standardised definition which is widely used, there is no accepted definition for remission. In defining remission, domains other than articular are seldom used and although patient's opinion is usually evaluated, it rarely includes domains other than pain or global assessment. The concept of remission remains un unmet need in PsA.
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Disclosure of Interest None declared
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