Objective: To create minimal disease activity (MDA) criteria for psoriatic arthritis (PsA). With recent therapeutic advances, this is now a goal for treatment and may represent a measure to compare therapies. It defines a satisfactory state of disease activity, rather than a change, and encompasses all aspects of disease.
Methods: 40 patient profiles were sampled from an observational PsA database. Sixty experts in PsA classified these as whether in MDA or not. A ≥70% consensus was accepted, identifying 13 profiles in MDA. Summary statistics created possible cut points for the definition. Considering the number of measures that must be met, 35 candidate definitions were created and tested using receiver operating characteristic curves (ROC) for sensitivity and specificity.
Results: Four candidate definitions showed high area under the curve values on ROC testing. Definitions with high outlying values were excluded as they were not considered to represent MDA. Aiming for high specificity to reduce false positives resulted in a preference for the following definition: A patient is classified as achieving MDA when meeting 5 of the 7 following criteria: tender joint count ≤1; swollen joint count ≤1; PASI ≤1 or BSA ≤3; patient pain VAS ≤15; patient global disease activity VAS ≤20; HAQ ≤0.5; tender entheseal points ≤1.
Conclusion: This study provides the first definition of a "state" of MDA in PsA and defines a target for treatment. It must now be validated in other populations and tested in clinical trials.
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