Background We aimed to evaluate the dynamics of treatment response with different composite measures in the TIght COntrol of inflammation in early Psoriatic Arthritis (TICOPA) trial.

Methods Participants with early disease-modifying antirheumatic drug-naïve psoriatic arthritis (PsA) were randomised 1:1 to either tight control (TC; 4 weekly review with therapy escalation if criteria not met) or standard care (SC; 12 weekly review). We calculated modified versions of the Psoriatic ArthritiS Disease Activity Score (PASDAS), Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) Composite scorE (GRACE) and Composite Psoriatic Disease Activity Index (CPDAI) at baseline and 12 weekly to 48 weeks by blinded assessor. For missing data, we used the last observation carried forward. Comparison between groups was made by analysis of covariance and comparison of area under the curve (AUC).

Results 206 people were randomised to TC (n=101) or SC (n=105). Significant differences between treatment groups were seen (p<0.0001 for all composite measures). AUC analysis demonstrated a significant difference between groups for the PASDAS but not GRACE and CPDAI. For participants with oligoarthritis, a significant difference between groups was seen for each measure, although the significance levels were greatly diminished (PASDAS, p=0.04; GRACE p=0.01; CPDAI p=0.04). For oligoarthritis using AUC analysis, none of the measures could distinguish between groups.

Conclusions Composite measures of disease activity were able to distinguish between TICOPA treatment arms, although differences were diminished for those with oligoarthritis. Further data are needed to inform the preferred composite measure for use as the primary outcome in PsA trials.

Trial registration number ClinicalTrials.gov (NCT01106079) and ISCRCTN registry (ISCRCTN30147736).