Male Sex Predicts a Favorable Outcome in Early ACPA-negative Rheumatoid Arthritis: Data From An Observational Study.

Objective The aim of the present study was to investigate if the relation between sex and clinical outcomes in early rheumatoid arthritis varies by autoantibody status.

Methods Two inception cohorts of consecutive patients with early RA (symptom duration ≤12 months) in the Southern Region of Sweden were investigated. Patients were stratified by anti-citrullinated peptide antibody (ACPA) status. The primary outcome was remission (DAS28<2.6) at 12 months. Secondary outcomes were remission at 6 months and EULAR good response compared to baseline at 6 and 12 months. In logistic regression models, adjusted for age, DAS28 and HAQ at baseline, the relation between sex and clinical outcomes, stratified by ACPA status, was investigated.

Results In total 426 patients with early RA were included, 160 ACPA-negative and 266 ACPA-positive. At 12 months, 27% of females and 24% of males with ACPA-positive RA achieved DAS28 remission. In ACPA-negative RA, 16% of females and 49% of males achieved DAS28 remission at 12 months. Males had higher odds of reaching remission at 12 months in the ACPA-negative patient group (pooled adjusted OR 4.79, 95% CI 1.97-11.6), but not in the ACPA-positive group (pooled adjusted OR 1.06, 95 % CI 0.49-2.30).

Conclusion Male sex was associated with better clinical outcomes in ACPA-negative early RA, but not in ACPA-positive early RA. The poor outcomes in females with early seronegative RA suggest that this represents a difficult to treat patient group.