Differences in disease activity measures in patients with rheumatoid arthritis who achieved DAS, SDAI, or CDAI remission but not Boolean remission

Abstract

Objectives: In patients with rheumatoid arthritis (RA), remission may be assessed by various composite measures. We assessed achievement of remission as defined by Boolean criteria, Simplified Disease Activity Index (SDAI), Clinical Disease Activity Index (CDAI), and 28-joint Disease Activity Score using C-reactive protein (DAS28[CRP]) and determined the components that limit patients in SDAI, CDAI, or DAS28(CRP) remission from achieving Boolean remission.

Methods: The proportions of patients achieving Boolean, SDAI, CDAI, or DAS28(CRP) remission were calculated for 3 trials: PREMIER and OPTIMA in patients with early RA and DE019 in patients with established RA. At the first visit that remission was recorded during the first 52 weeks of the trial, the following were assessed: swollen/tender joint count at 28 and 66/68 joints, CRP, Patient's/Physician's Global Assessment (PGA/PhGA), SDAI, DAS28(CRP), and Health Assessment Questionnaire-Disability Index.

Results: The majority of patients (61-66%) who achieved SDAI or CDAI remission also attained Boolean remission. Although DAS28(CRP) remission was most frequently attained, 74-77% of patients in DAS28(CRP) remission did not achieve Boolean remission. Compared with patients in Boolean remission, patients in SDAI or CDAI remission but not Boolean remission had higher PGA scores, while patients with DAS28(CRP) remission but not Boolean remission had higher joint counts, and PGA and PhGA scores.

Conclusions: Differences in PGA limit patients in SDAI/CDAI remission from meeting the Boolean remission criteria, suggesting that these criteria otherwise can be used interchangeably. In contrast, patients in DAS28(CRP) remission are limited by differences in multiple disease activity measures from achieving Boolean remission.

Keywords: Anti-TNF; Boolean remission; CDAI; Disease activity; Rheumatoid arthritis; SDAI.