Background/Purpose: No single “gold standard” measure is available to assess patients with rheumatoid arthritis (RA) in clinical trials and routine care, as in hypertension, diabetes, and other diseases. Therefore, an index of several measures, such as a DAS28 (Disease Activity Score-28) and CDAI (Clinical Disease Activity Index), based on 7 RA core data set measures, is needed. However, the only quantitative data collected in many (most) patients at routine rheumatology care visits are laboratory tests. RAPID3 (routine assessment of patient index data), which includes only patient self-report scores, is considerably more feasible than DAS28 or CDAI for routine care, distinguishes active from control treatments in RA clinical trials similarly and is correlated significantly with these indices. A minimal clinically important improvement (MCII) to aid in planning and interpretation of changes in disease activity/severity in clinical trials as well as in routine care has not been established for RAPID3, and is presented here.

Methods: Post hoc analyses were performed of a longitudinal study of 250 patients with active RA, in whom results of treatment escalation were assessed quantitatively, as described previously (1). All 7 RA core data set measures were collected at baseline and after treatment escalation. RAPID3 is the sum of 3 0-10 measures for a 0-10 (converted from 0-3) physical function scale and 0-10 visual analog scales (VAS) for pain and patient global assessment, total=0-30. DAS28-ESR and CDAI were computed as described in the literature. Patient judgment of improvement was recorded independently as “improved”, “the same” or “worsened”, and dichotomized as improved vs same/worsened to generate receiver operating characteristic (ROC) curves, to determine MCIIs as changes that had a specificity of 0.80 for improvement. Sensitivity to change was assessed as standardized response means (SRM).

Results: Among 250 patients, 167 (66.8%) reported improvement. Each composite index was sensitive to change, with SRMs ranging from -0.79 to -0.98 (Table). The mean ROC curve area ranged from 0.77 for DAS28-ESR to 0.80 for RAPID3 (Table). With a criterion of a specificity of 0.80, the MCIIs were -3.5 for RAPID3, -1.17 for DAS28-ESR, and −12.5 for CDAI. MCIIs were in a similar range of 11.6% to 16.8% of maximum score (Table).

Conclusion: MCIIs for RAPID3 were similar in ROC curve areas and SRM to DAS28 and CDAI. Knowledge concerning MCII thresholds can improve planning and interpretation of data from clinical trials and routine clinical care.

References: 1. Ward, M et al, Ann Rheum Dis 2015, 74:1691–1696

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/minimal-clinically-important-improvement-mcii-of-rapid3-routine-assessment-of-patient-index-data-3-an-index-of-only-patient-self-report-scores-in-rheumatoid-arthritis-ra-similar-performa/