Background RAPID3 is a patient completed outcome measure assessing disease activity in inflammatory arthritis consisting of the health assessment questionnaire (HAQ) and two VAS scales. It is feasible for use in clinical practice and has been well validated in rheumatoid arthritis (RA) and other conditions, but there is little data on its use in psoriatic arthritis (PsA).
Objectives To investigate the responsiveness and discrimination of RAPID3 and a modified version with skin VAS in the Tight Control of Psoriatic Arthritis (TICOPA) trial.
Methods Data from the TICOPA trial were used to assess the performance of the RAPID3 index. RAPID3 was calculated using the HAQ-DI, patient completed pain VAS and global disease activity VAS. Due to concerns about skin involvement in PsA, we also calculated a novel RAPID3Ps score which also included a skin activity VAS to see if performance was superior.
Results from the RAPID3 measures were correlated with the PsA disease activity score (PASDAS) a composite disease activity score already validated by GRAPPA. Change in the RAPID3 measures and other outcome measures were compared between the tight control arm and the standard care arm of the TICOPA study using t-test for continuous variables and chi-squared for categorical measures of disease state.
Results RAPID3 scores strongly correlated with PASDAS (Pearson correlation 0.794, p<0.01) at all baseline and follow up visits. The change in score at follow up was also moderately correlated with the change in PASDAS (0.636, p<0.01). Correlation was similar for the RAPID3Ps at 0.831.
When looking at differentiation between treatment groups, change in RAPID3 score at 48 weeks was highly discriminant (t value -3.43, p<0.001) and was higher than all other PsA measures (DAPSA and other individual outcome measures) except for PASDAS (t value -3.75, p<0.001) as shown in the table.
Looking at specific cutpoints, RAPID3 “near remission” was also highly discriminant between treatment groups (chi squared 7.48, p=0.006) although with a lower value than the minimal disease activity criteria for PsA (chi squared 10.11, p=0.001).
Conclusions RAPID3 shows good correlation with other validated measures of disease activity in PsA and addition of a psoriasis measure does not seem necessary in this population. The RAPID3 score and “near remission” definition are able to effectively discriminate between two active treatment groups in an interventional trial.
Acknowledgement We acknowledge all collaborators and participants in the TICOPA trial.
Disclosure of Interest None declared
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