Clinical outcomes of patients with active rheumatoid arthritis with normal acute phase reactant values

Aim: Despite high clinical disease activity, some patients with active rheumatoid arthritis (RA) have normal acute phase reactant (APR) values. This study aimed to determine the clinical outcomes of active RA patients with normal APR values. Method: Of 5376 patients with RA enrolled in the Korean observational study network for arthritis (KORONA) registry, 400 patients with disease duration of <2 years who had Clinical Disease Activity Index (CDAI) score of >2.8 at baseline, biologic-naïve, and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) drawn at both baseline and 2-year follow-up visits were identified. Patients were grouped according to baseline APR levels: normal APRs, one APR elevated, and both APRs elevated. Results: Baseline tender and swollen joint counts, mean CDAI and Health Assessment Questionnaire-Disability Index (HAQ-DI) scores were significantly lower in the normal APRs group compared with APR-elevated groups (P < 0.0001). At 2-year follow-up, mean CDAI scores, HAQ-DI, and percentage of the patient achieving remission were not significantly different between the normal APRs group compared with the APR-elevated groups regardless of the baseline disease activity. However, in patients with baseline CDAI moderate to high disease activity, the normal APRs group less frequently required initiation of the biologic disease-modifying anti-rheumatic drugs compared with the APR-elevated groups (P = 0.044). Conclusion: Active RA patients with normal APR values have milder disease presentation, but similar clinical outcomes to those with elevated APRs.