Routine Assessment of Patient Index Data 3 (RAPID3) alone is insufficient to monitor disease activity in rheumatoid arthritis in clinical practice

Objective To test the longitudinal association between patient-reported outcome, Routine Assessment of Patient Index Data 3 (RAPID3) and the Disease Activity Score in 28 joints that includes the erythrocyte sedimentation rate (DAS28-ESR) in routine-care patients with rheumatoid arthritis (RA). Methods Patients with RA treated with disease-modifying antirheumatic drugs were included in this prospective observational cohort. The longitudinal association between RAPID3 (0-10) and DAS28-ESR and its individual components (swollen joint count (SJC), erythrocyte sedimentation rate (ESR) (mm/hour), tender joint count (TJC) and patient global assessment (PGA)) was tested using generalised estimating equations in patients with more than two consecutive visits with data on RAPID3 and DAS28-ESR. Interactions between RAPID3 and gender, pain, PGA and age at baseline were tested, and if significant (p<0.20) and clinically relevant, models were fit in the corresponding strata. Results In total, 330 patients were included (mean follow-up 10.7 (SD 9.7) months, female gender 67.9%). The longitudinal association between RAPID3 and DAS28-ESR was weak (β=0.29 (95% CI 0.24 to 0.35), n=207), meaning that one unit increase in RAPID3 corresponded to a 0.29 unit increase in Disease Activity Score in 28 joints (DAS28). RAPID3 was most strongly associated with subjective (TJC: β=0.89 (95% CI 0.61 to 1.17); PGA: β=0.94 (95% CI 0.84 to 1.04)) and not with objective components of DAS28 (SJC: β=0.29 (95% CI 0.17 to 0.41), n=172). The association between RAPID3 and ESR was poor but modified by gender, being only significant in men (β=0.37 (95% CI 0.08 to 0.67)). Conclusions These data suggest that RAPID3 does not sufficiently capture changes in objective inflammatory signs. Monitoring by RAPID3 alone is therefore insufficient to follow disease activity in patients wth RA in clinical practice.