Further Optimization of the Reliability of the 28-Joint Disease Activity Score in Patients with Early Rheumatoid Arthritis

Abstract

BackgroundThe 28-joint Disease Activity Score (DAS28) combines scores on a 28-tender and swollen joint count (TJC28 and SJC28), a patient-reported measure for general health (GH), and an inflammatory marker (either the erythrocyte sedimentation rate [ESR] or the C-reactive protein [CRP]) into a composite measure of disease activity in rheumatoid arthritis (RA). This study examined the reliability of the DAS28 in patients with early RA using principles from generalizability theory and evaluated whether it could be increased by adjusting individual DAS28 component weights.MethodsPatients were drawn from the DREAM registry and classified into a “fast response” group (N = 466) and “slow response” group (N = 80), depending on their pace of reaching remission. Composite reliabilities of the DAS28-ESR and DAS28-CRP were determined with the individual components' reliability, weights, variances, error variances, correlations and covariances. Weight optimization was performed by minimizing the error variance of the index.ResultsComposite reliabilities of 0.85 and 0.86 were found for the DAS28-ESR and DAS28-CRP, respectively, and were approximately equal across patients groups. Component reliabilities, however, varied widely both within and between sub-groups, ranging from 0.614 for GH (“slow response” group) to 0.912 for ESR (“fast response” group). Weight optimization increased composite reliability even further. In the total and “fast response” groups, this was achieved mostly by decreasing the weight of the TJC28 and GH. In the “slow response” group, though, the weights of the TJC28 and SJC28 were increased, while those of the inflammatory markers and GH were substantially decreased.ConclusionsThe DAS28-ESR and the DAS28-CRP are reliable instruments for assessing disease activity in early RA and reliability can be increased even further by adjusting component weights. Given the low reliability and weightings of the general health component across subgroups it is recommended to explore alternative patient-reported outcome measures for inclusion in the DAS28.

Fluorescence optical imaging for treatment monitoring in patients with early and active rheumatoid arthritis in a 1-year follow-up period

“…In addition, Werner et al suggested divergence between local inflammation in the hand and systemic inflammation [21]. Furthermore, high variance for components of the DAS28 was recently described [37], while FOI is a more objective technical tool.…”

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“…These include DAS28 remission (< 2.6), structural remission on radiology imaging, immunological remission, low co-morbidity index, medication remission and patient defined remission [ 32 ]. DAS28-ESR, recommended by EULAR for RA disease activity measurement, showed a composite reliability of 0.86 [ 33 ]; however, the subjective parameters of the scoring system make it less reliable [ 34 ]. The other scoring systems for assessing RA disease activity include the clinical disease activity index (CDAI) and simplified disease activity index (SDAI).…”

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“…Der DAS-28 ist ein validierter Score, bei dem hauptsächlich die Gelenke der oberen Extremitäten beurteilt werden. Allerdings deuten viele Studien auf eine Unzulänglichkeit und hohe Variabilität des DAS-28-Scores in der Erfassung des Handstatus hin [22,25,26]. Siemons et al beschrieben beispielsweise eine hohe Varianz für Komponenten des DAS-28 [26].…”

“…Allerdings deuten viele Studien auf eine Unzulänglichkeit und hohe Variabilität des DAS-28-Scores in der Erfassung des Handstatus hin [22,25,26]. Siemons et al beschrieben beispielsweise eine hohe Varianz für Komponenten des DAS-28 [26]. Darüber hinaus berichten sogar Patient*innen in einer nach DAS-28-Score definierten Remission von Einschränkungen der Handfunktion und Behinderungen bei täglichen Aufgaben [5].…”