Discrepancy Between Multibiomarker Disease Activity and Clinical Disease Activity Scores in Patients With Persistently Active Rheumatoid Arthritis

Objective Responsive assessment of disease activity in patients who have rheumatoid arthritis (RA) is necessary to evaluate therapeutic efficacy and guide treatment. We compared the utility of the multibiomarker disease activity (MBDA) score in the assessment of RA disease activity with that of the Disease Activity Score in 28 joints using the erythrocyte sedimentation rate (DAS28-ESR) score and the Clinical Disease Activity Index (CDAI) in a multicenter, randomized, placebo-controlled trial of repository corticotropin injection (RCI) in patients with persistently active RA. Methods Patients received 80 units of RCI twice weekly during a 12-week open-label period; those who experienced low disease activity at week 12 were randomly assigned to receive either 80 units of RCI or placebo twice weekly during a 12-week double-blind period. Changes in disease activity (measured by DAS28-ESR, CDAI, and MBDA scores) and correlations between MBDA scores and both DAS28-ESR and CDAI scores were assessed. Results Changes from baseline in DAS28-ESR and CDAI scores suggested that RCI therapy led to clinically meaningful improvements in disease activity, but improvements from baseline in MBDA scores were below the minimally important difference threshold. For the DAS28-ESR and CDAI, correlations with total MBDA and individual component scores were generally low (r <= 0.3) and occasionally moderate (r > 0.3 but r < 0.5). Conclusion The results of the present study suggest overall MBDA scores are not sufficiently responsive for assessing RA disease activity after RCI therapy. These findings are consistent with those seen with other RA drugs and, although they are from a clinical trial, suggest the MBDA should not be a preferred disease activity measure in clinical practice.