Background Minimal disease activity (MDA) is defined by OMERACT as “that state of disease activity deemed a useful target of treatment by both the patient and physician, given current treatment possibilities and limitations” and criteria for MDA in psoriatic arthritis (PsA) have been developed using consensus opinion of international experts.
Objectives The aim was to investigate if the criteria correlated well with the opinion of rheumatologists treating PsA and their patients and investigate how they compare with other composite outcome measures in development for PsA.
Methods The study was an analysis of baseline visits for patients in the GRACE study, an international observational cohort recruited to develop new outcome measure in PsA. At baseline, data on all aspects of disease activity and patient reported outcomes were collected. The treating physician was asked “Do you think this patient is in an MDA state?” and the patient was asked “Do you think your disease is well controlled?” Patients were classified as MDA if they fulfilled 5 of 7 from: tender joint count≤1; swollen joint count≤1; psoriasis activity and severity index≤1 or body surface area≤3; patient pain visual analogue score (VAS)≤15; patient global disease activity VAS≤20; health assessment questionnaire≤0.5; tender entheseal points≤1. ROC analysis was used to test the MDA criteria using physician and patient opinion as the gold standard. Composite measure scores for those patient in MDA and those not were compared and tested using Mann-Whitney U statistics.
Results In total, data on 503 patients were collected at baseline. Using the physician’s opinion as a gold standard, the MDA criteria performed well with an area under the curve of 0.82 (95% CI 0.79, 0.86, p<0.001). Using the proposed cut-off of 5 gave a sensitivity of 40.3% and a specificity of 97%. Using the patient’s opinion as a gold standard, the MDA criteria also performed well with an AUC of 0.80 (95% CI 0.76, 0.84, p<0.001). Again the specificity of the criteria was high (98%) but sensitivity was also lower (33%).
Comparison was made with proposed composite outcome measures for PsA including the CPDAI, DAPSA, PASDAS and AMDF. Scores for those in MDA and those not showed good separation for all of these composite measures (p<0.001) with the highest z-statistics for the AMDF and CPDAI.
Conclusions The MDA criteria for PsA correlate well with both physician and patient opinion in a large real-life observational cohort. The criteria had a high specificity for identifying patients with adequate disease control meaning that patients would not be undertreated using these criteria. The lower sensitivity identifies some patients who did not fulfil the criteria, but were still felt to have good disease control, identifying a tolerance by both physicians and patients for mild levels of disease activity in multiple domains of PsA.
Disclosure of Interest None Declared