Monitoring Rheumatoid Arthritis Disease Activity

Recommended Disease Activity Measures

The American College of Rheumatology recommends using one of six validated composite disease activity measures for monitoring RA: CDAI, DAS28 (ESR or CRP), PAS, PAS-II, RAPID-3, or SDAI, with selection based on practice setting's resources and feasibility 1, 2, 3
The ACR systematically evaluated 63 available RA monitoring tools and narrowed them to 6 validated measures that produce continuous indices with defined thresholds for remission, low, moderate, and high disease activity 1, 2, 3
RAPID-3 is a patient-reported measure that includes patient pain, patient global assessment, and Multidimensional HAQ, which can be completed in less than 3 minutes 1, 4
PAS-II is a patient-reported measure that includes patient pain, patient global assessment, and HAQ-II 1, 4
PAS is a patient-reported measure that includes patient pain, patient global assessment, and original HAQ 1, 4
CDAI is a provider-assessed measure that includes 28 tender joint count, 28 swollen joint count, patient global assessment, and provider global assessment, without requiring lab results 4, 5
SDAI is a provider-assessed measure that includes CDAI plus CRP, requiring lab results 4, 5
DAS28 is a complex formula that incorporates 28 tender/swollen joint counts, patient global assessment, and ESR or CRP 1, 2

CDAI has defined thresholds for remission (≤2.8), low disease activity (>2.8 to 10.0), moderate disease activity (>10.0 to 22.0), and high disease activity (>22.0) 5
SDAI has defined thresholds for remission (≤3.3), low disease activity (>3.3 to ≤11.0), moderate disease activity (>11.0 to ≤26), and high disease activity (>26) 5

The American College of Rheumatology recommends measuring disease activity every 1-3 months until remission is achieved, and every 3-6 months once remission/low disease activity is achieved 6

ESR and CRP are incorporated into DAS28-ESR, DAS28-CRP, and SDAI scores, though these measures are not interchangeable 6
Baseline labs should include ESR, complete blood count, transaminases, renal function, and urinalysis 6

Choose a disease activity measure based on practice resources, such as RAPID-3 for limited time/no joint count training, CDAI for can perform joint counts but no immediate lab access, or SDAI/DAS28 for full resources with lab access 1, 2, 4, 5
Establish a baseline score at diagnosis and monitor systematically every 1-3 months during active disease and every 3-6 months once remission/low disease activity is achieved 1, 2, 5, 6

The American College of Rheumatology recommends monitoring RA patients with validated disease activity measures every 1-3 months during active disease and every 3-6 months once remission or low disease activity is achieved, combined with medication-specific laboratory surveillance based on DMARD regimen 7, 8
Measure functional status at least annually using standardized tools, but increase frequency to match disease activity assessments when disease is active 7, 8
Continue using the same composite measure for consistency once a disease activity measure is selected 7, 8
Don't switch validated measures arbitrarily, as this can affect longitudinal tracking 7, 8
Don't allow payer-driven medication switching when patients have achieved low disease activity or remission 7, 8

Monitor CBC, liver transaminases, and serum creatinine every 2-4 weeks for the first 3 months or after dose increase, every 8-12 weeks for months 3-6 on stable therapy, and every 12 weeks beyond 6 months on stable therapy for methotrexate, leflunomide, and sulfasalazine 9
Don't use less frequent monitoring intervals prematurely, maintain every 2-4 week laboratory monitoring for the full first 3 months on methotrexate, leflunomide, or sulfasalazine 9