CLINICAL OUTCOMES OF PATIENTS WITH ACTIVE RHEUMATOID ARTHRITIS WITH NORMAL ACUTE PHASE REACTANT VALUES

Abstract

Background Some patients with active rheumatoid arthritis (RA) have normal acute phase reactant (APR) values despite high clinical disease activity measured by joint counts and global assessments. This group of patients may have different clinical outcomes compared with patients with elevated APRs in regards that they might have less aggressive disease or disease activity might be underestimated since Disease Activity Score (DAS)28 used in routine clinical practice includes an APR in its scoring.

Objectives The objective of this study was to determine the clinical outcomes of patients with clinically active RA but has normal APR values enrolled in the KORean Observational study Network for Arthritis (KORONA).

Methods Of 2,583 patients with RA, 400 patients who had the duration within 2 years, the Clinical Disease Activity Index (CDAI) score of >2.8 at baseline, biologics-naive, and ESR and CRP drawn at both baseline and two year follow-up visit were identified. Patients were grouped according to baseline APR levels; neither elevated ESR nor CRP (normal APRs), either ESR or CRP elevated (one APR positive), and both elevated ESR and CRP (both APRs positive).

Results Of 400 patients with active RA, 39% had normal APRs; 27% had one APR positive; only 34% had both APRs positive. The APR groups did not differ in baseline age, sex, disease duration, socioeconomic status, and positivity for rheumatoid factor or anti-cyclic citrullinated peptide antibody. Baseline disease activity measured by tender and swollen joint counts, DAS28, CDAI, and Health Assessment Questionnaire Disability Index (HAQ-DI) score were significantly lower in normal APRs group compared with APRs positive group. At two-year follow-up, DAS28, CDAI score, and HAQ-DI score were significantly lower in normal APRs group. Patients with normal APRs were less likely to use glucocorticoids and biologics. Significantly more patients in normal APRs group achieved remission defined by DAS28 compared with one APR or both APRs positive groups (51.7% vs 34.34% vs 28.7%, p=0.0003). However, remission rate defined by CDAI was comparable in all 3 APR groups.

Conclusions Active RA patients with normal APRs have milder disease, require less aggressive treatment, and better clinical outcomes compared with APRs positive patients. Composite disease activity measures which do not include APRs in its scoring should be considered for monitoring disease activity in normal APRs group because of the risk of misclassification for disease activity by DAS28.