Background/Purpose: Adult-onset Still’s disease (AOSD) is a rare systemic inflammatory disorder of unknown aetiology usually affecting young adults. Despite the evidence increasingly reporting the efficacy of therapies, an agreement concerning the disease activity assessment is still missing and individual empirical definitions are used, due to the lack of validated clinical tools. Thus, we aimed to develop the European League Against Rheumatism (EULAR) score for the definition of AOSD disease activity (the DAVID score).

Methods: Firstly, a systematic literature review (SLR) was performed to retrieve the clinical variables associated with AOSD disease activity and 3 Delphi rounds were performed to collect experts’ opinions. Subsequently, in a prospective study, the selected features were assessed at baseline, after 3-, and 6-months in AOSD patients, included in the Gruppo Italiano Di Ricerca in Reumatologia Clinica e Sperimentale (GIRRCS) AOSD-study group from January 2022 and December 2023. Each patient was scored as being either “active” or in “remission” based on the clinical judgement of the physician in charge for the management. The final selection of the items for the score was based on the findings derived by correlations between the clinical characteristics and disease activity as scored by physicians, principal components analysis, the coefficients of a linear model with disease activity being the dependent variable, and expert opinion. A rule-based algorithm was subsequently produced to define the disease activity. We assessed model performance using area under the Receiver Operation Characteristic (AUROC) curves.

Results: We analysed 187 complete pseudonymized AOSD patients (mean age 40.8±17.3 years) with available data at baseline, 3- and 6-month visits. The domains fever (yes/no), skin rash (yes/no), arthritis (yes/no), patient global assessment (in cm) and CRP in either mg/L or a binary format >5mg/L or >10mg/L were selected for the score. We achieved the highest AUROC for a binary CRP variable >10mg/L. For the patient global assessment, we defined ≥5cm as threshold for active disease; this was a pragmatic decision. Ratings at baseline and months 3 and 6 showed different cut-offs of the new DAVID score, implying the existence of two thresholds, one between remission and low disease activity and another one between low disease activity and active disease. The active disease was defined as the patient with either fever and one out of the following criteria: skin rash, arthritis, CRP >10mg/L, patient global ≥5cm or no fever and at least three of them (AUROC: 0.900), excluding possible diverse causes of fever (i.e., infective and neoplastic diseases, others). The low disease activity was defined by the absence of fever and at maximum one the following criteria: skin rash, arthritis, CRP >10mg/L, patient global ≥5cm (AUROC: 0.848). The remission was defined as the patient characterized by the absence of fever and none of the other above-mentioned criteria.

Conclusion: The EULAR disease activity score was developed for the definition of AOSD disease activity (the DAVID score) to be readily, reliable, and easily applied in any clinical setting to improve the patient management.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-development-of-the-eular-score-for-the-definition-of-disease-activity-in-adult-onset-stills-disease-the-david-project/