Background/Purpose:  In 2013, Treat to Target (T2T) in SpA Recommendations by expert consensus stated that the target of treatment should be remission or inactive disease. The only data in PsA is the Tight Control of PsA (TICOPA) trial which confirmed that T2T using a target of minimal disease activity (MDA) was superior to standard care. However MDA is not remission. Potential definitions that would fit with the T2T Recommendations would be MDA meeting all 7 cut points, proposed as a definition of very low disease activity (VLDA), or the Disease Activity in PsA (DAPSA) remission cut point. Our aim was to investigate which patients achieve definitions of remission and VLDA and how much residual active disease is still present.

Methods: This analysis uses data from the TICOPA study where 206 patients with newly diagnosed PsA were randomised 1:1 to receive either tight control (4 weekly review and treatment escalated until in MDA) or standard care (12 weekly review, no protocol for treatment). Three potential definitions of remission/inactive disease were used

• VLDA where all 7 of the MDA cut points are met: tender joint count (TJC)≤1; swollen joint count (SJC)≤1; enthesitis count≤1; PASI≤1; patient global visual analogue scale (VAS)≤20mm; patient pain VAS≤15; and health assessment questionnaire≤0.5.
• DAPSA remission where DAPSA≤4 (TJC + SJC + patient global VAS (cm) + physician global VAS (cm) + CRP (mg/l)
• Clinical DAPSA remission where DAPSA≤4 (TJC + SJC + patient global VAS (cm) + physician global VAS)

Results: At the end of the TICOPA study (48 weeks), 50 patients were in DAPSA remission, 58 in cDAPSA remission and 27 met VLDA. Unsurprisingly, the highest correlation in remission definitions was found between DAPSA and cDAPSA (Pearsons 0.927) with lower correlation between both DAPSA/cDAPSA and VLDA (0.609/0.593). The percentage exact agreement (PEA) for VLDA and the DAPSA/cDAPSA remission was 85.2/83.0% respectively. There were 25 people considered to be in DAPSA remission and 30 in cDAPSA remission who did not meet the VLDA cut off. In contrast only 2 people were not in DAPSA remission but did meet the VLDA cut off. Levels of residual active disease in patients meeting the remission/very low disease activity criteria are shown in the table. All definitions had similar proportions of people with residual disease but lower disease activity was seen in VLDA definition, particularly for swollen joint count and enthesitis as each domain had to score ≤1. All definitions had similar proportions of patients with raised CRP levels despite the CRP not being included in two of the definitions.

Conclusion:  The VLDA criteria are more stringent than both DAPSA and cDAPSA remission, with a lower number of people meeting this definition and less residual disease activity. The inclusion of a laboratory marker seems unnecessary in the definition as high CRP levels are similar in all definitions, making target assessment easier in clinical practice.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/what-should-be-the-primary-target-of-treat-to-target-in-psa/