Background/Purpose: PASDAS is a composite disease activity measure (range 0–10) for psoriatic arthritis (PsA). Recently, PASDAS disease activity cutoffs were proposed and a minimal disease activity (MDA) state for PsA was also defined as a target for treatment. We aimed to establish a cutoff value of PASDAS that defines MDA state, to validate previously defined PASDAS cutoffs for low and high disease activity (3.2 and 5.4), and to define PASDAS cutoffs reflecting disease activity in our cohort.

Methods: All patients meeting CASPAR criteria were prospectively recruited from a PsA clinic and items necessary to complete the PASDAS and the MDA were evaluated. For aim 1, ROC curve analysis determined the optimal PASDAS cutoff discriminating patients based on MDA state. This analysis was subsequently repeated twice changing the discriminating criteria to meeting 6 of 7 and all 7 of the 7 MDA criteria. For aim 2 sensitivity and specificity of the previously defined PASDAS cutoffs for high and low disease activity were determined. For aim 3 patients were dichotomized based on the decision to escalate treatment by the treating physician (indicator of high disease activity). ROC curve analysis (90% specificity) estimated the PASDAS cutoff for high disease activity. Further, the median value of PASDAS for each treatment change group estimated PASDAS cutoffs for low and high disease. Lastly, ROC curves (90% specificity) estimated PASDAS cutoffs using patient’s global assessment of disease activity (PGA) as an external standard (<10 low; ≥10 moderate <60; ≥60 high). The mean values obtained by the 3 methods defined the final PASDAS cutoffs.

Results: 178 patients [53.9% male, mean age 56.8 years, disease duration 17.6 years, mean (SD) PASDAS 3.29 (1.29), 48.9% in MDA] were recruited. See table 1. PASDAS of <3.2 defined MDA (AUC- 0.96, sensitivity 88% [95% CI: 80-93%], specificity 92% [95% CI: 84-96%], Youden index- 0.80). For MDA based on meeting 6 of 7 criteria and all 7 of 7 criteria PASDAS scores of 2.6 and 2.1 maximized sensitivity and specificity, respectively. The published PASDAS cutoffs showed the following sensitivities and specificities (%), respectively: low- 100, 56; high- 12, 99 (PGA as external criterion). ROC curve analysis using treatment escalation as discriminating variable estimated a PASDAS high disease activity cutoff of 4.7 (AUC- 0.76). Median PASDAS of escalation and no-escalation groups were 4.17 and 2.86, respectively. When using PGA, PASDAS cutoffs for low and high disease were 2.08 (AUC- 0.95) and 4.14 (AUC- 0.93), respectively. The final PASDAS cutoffs (mean of 3 methods) for low and high disease activity cutoffs were 2.5 and 4.3, respectively.

Conclusion: A PASDAS score <3.2 reflects MDA. MDA based on stricter criteria may better reflect low disease activity state. Previously defined PASDAS cutoff for low disease activity state has high sensitivity while high disease activity cutoff has high specificity. Our cohort produced lower cutoffs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/treating-psoriatic-arthritis-psa-to-target-defining-psoriatic-arthritis-disease-activity-score-pasdas-that-reflects-disease-activity-in-psa/