Determination of the most appropriate ACR response definition for contemporary drug approval trials in rheumatoid arthritis.

OBJECTIVES: To evaluate which American College of Rheumatology (ACR) response definition (ACR20, 50 or 70) should primarily be used for efficacy claims in future drug approval trials of rheumatoid arthritis (RA). METHODS: We systematically searched EMBASE, Medline and the Cochrane Library for randomised controlled RA drug approval trials of biological and targeted synthetic disease-modifying antirheumatic drugs (DMARDs). We included full-text articles reporting ACR response rates for multiple time points over a 24-week placebo-controlled period and visualised normalised response trajectories over time in different patient populations. Using mixed-effect logistic regression, we calculated the proportion of ACR responders per outcome and time point, and compared the discriminant validity of these metrics at multiple time points. RESULTS: We screened 12 680 records and included 45 in the final analysis. Discriminative capacity of the ACR20 was high across all time points, whereas ACR50 and ACR70 showed highest discrimination towards the end of the placebo-controlled periods. This effect could be observed in all patient populations and compound groups. Faster response to treatment was observed in DMARD naïve patient populations when compared with DMARD insufficient responders. CONCLUSION: ACR20 remains the most powerful discriminator between active treatment and placebo, especially when early discrimination is of primary interest. At the same time, our results support the selection of more stringent thresholds if later time points shall be evaluated, given their comparable discriminant but higher clinical face validity.

Definition of rheumatoid arthritis flare based on SDAI and CDAI.

OBJECTIVE: To develop and validate definitions for disease flares in rheumatoid arthritis (RA) based on the quantitative Simplified and Clinical Disease Activity Indices (SDAI, CDAI). METHODS: We analysed RA treatment courses from the Norwegian disease-modifying antirheumatic drug registry (NOR-DMARD) and the Vienna RA cohort. In a receiver operating curve analysis, we determined flare definitions for absolute changes in SDAI and CDAI based on a semiquantitative patient anchor. NOR-DMARD was sampled into an 80%-training cohort for cut point derivation and a 20%-test cohort for internal validation. The definitions were then externally validated in the independent Vienna RA cohort and tested regarding their performance on longitudinal, content, face, and construct validity. RESULTS: We analysed 4256 treatment courses from NOR-DMARD and 2557 from the Vienna RA cohort. The preliminary definitions for absolute changes in SDAI and CDAI for flare are an increase of 4.7 and 4.5, respectively. The definitions performed well in the test and external validation cohorts, and showed clinical face and construct validity, as flares significantly impact both functional ( ∆ Health Assessment Questionnaire flare vs no-flare +0.43; p<0.001) and structural ( ∆ modified Sharp Score 43% higher after flare; p<0.001) disease outcomes, and reflect consistent worsening across all disease core sets, both patient reported and objective. CONCLUSION: We here provide novel definitions for flare in RA based on SDAI and CDAI, validated in two large independent real-world cohorts. In times of highly effective medications for RA, and consideration of their tapering, these definitions will be useful for guiding decision making in clinical practice and designing clinical trials.

Tenderness and radiographic progression in rheumatoid arthritis and psoriatic arthritis.

OBJECTIVE: The aim of this study was to assess the predictive value of tenderness in the absence of swelling with consideration of other potential risk factors for subsequent radiographic progression in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). METHODS: Clinical and sonographic (grey scale and power Doppler (PD)) examination of 22 joints of the hand were performed in patients with RA and PsA. The impact of tenderness on progression after 2 years was analysed in non-swollen joints for RA and PsA separately with multilevel mixed logistic regression analysis. RESULTS: We included 1207 joints in 55 patients with RA and 352 joints in 18 patients with PsA. In RA, tenderness was associated with radiographic progression after 2 years (model 2: OR 1.85 (95% CI 1.01 to 3.27), p=0.047), although the association of PD (OR 2.92 (95% CI 1.71 to 5.00), p<0.001) and erosions (OR 4.74 (95% CI 2.44 to 9.23), p<0.001) with subsequent structural damage was stronger. In PsA, we found a positive but not significant association between tenderness and radiographic progression (OR 1.72 (95% CI 0.71 to 4.17), p=0.23). In contrast, similarly to RA, erosions (OR 4.62 (95% CI 1.29 to 16.54), p=0.019) and PD (OR 3.30 (95% CI 1.13 to 9.53), p=0.029) had a marked effect on subsequent structural damage. CONCLUSION: Our findings imply that tenderness in non-swollen joints in RA is associated with subsequent damage. In both diseases, additional risk factors, such as sonographic signs for synovitis and baseline radiographic damage are associated with radiographic progression.