Validation of the Disease Activity Index for PSoriatic Arthritis (DAPSA) with a quick quantitative C-reactive protein assay (Q-DAPSA) in patients with psoriatic arthritis (PsA)
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The Disease Activity Index for PSoriatic Arthritis (DAPSA) is a validated, unidimensional score focusing on joint involvement and is one of the recommended options to assess disease activity in psoriatic arthritis (PsA) patients (1). It involves clinical parameters and a C-reactive protein (CRP) value (2, 3). However, determination of routine laboratory CRP values takes several hours. Thus, the clinical DAPSA (cDAPSA), omitting CRP values, has been proposed as an alternative for clinical routine (3, 4). Quick quantitative CRP (qCRP) tests only require a few minutes and might serve as another appropriate option to calculate the DAPSA (as Q-DAPSA) in clinical routine. Therefore, this study aimed to validate the Q-DAPSA in a multicenter PsA cohort.
PsA patients were recruited from five centers within Berlin, Germany. All patients received a rheumatological assessment, including patient reported outcomes (PROs). Routine laboratory CRP was measured in certified laboratories, qCRP values and erythrocyte sedimentation rate (ESR) values were measured locally at the study centers. The qCRP testing was performed with the „QuikRead go instrument“ (Aidian Oy, Espoo, Finland). The statistical analysis included descriptive statistics as well as cross tabulations and weighted Cohen´s kappa to compare disease activity categories. Bland-Altman plots and intraclass correlation coefficients (ICC) were used to analyse the agreement of numerical values by routine laboratory CRP vs. qCRP and different DAPSA scores.
In total, 104 patients were included in the statistical analysis. Recruitment was performed between January and October 2020. Q-DAPSA and DAPSA showed identical disease activity categories in 102 of 104 (98.1%) patients with a weighted Cohen´s kappa of 0.980 (95% CI: 0.952; 1.000). The cDAPSA showed identical disease activity categories compared to DAPSA in 97 of 104 (93.3%) patients with a weighted Cohen´s kappa of 0.932 (95% CI: 0.885; 0.980).
In conclusion, DAPSA and Q-DAPSA showed almost absolute agreement regarding identical disease activity categories. The agreement between DAPSA and cDAPSA disease activity categories was slightly lower, but also very high. The Q-DAPSA can be determined quickly in clinical routine and has the additional benefit of involving an acute phase parameter. As a consequence, the Q-DAPSA could facilitate the implementation of a treat-to-target concept in PsA patients.
- Smolen JS et al. Treating axial spondyloarthritis and peripheral spondyloarthritis, especially psoriatic arthritis, to target: 2017 update of recommendations by an international task force. Ann Rheum Dis 2018.
- Nell-Duxneuner et al. Evaluation of the appropriateness of composite disease activity measures for assessment of psoriatic arthritis. Ann Rheum Dis 2010.
- Schoels M et al. Application of the DAREA/DAPSA score for assessment of disease activity in psoriatic arthritis. Ann Rheum Dis 2010.
- Schoels MM et al. Disease activity in psoriatic arthritis (PsA): defining remission and treatment success using the DAPSA score. Ann Rheum Dis 2016.