Diagnostic spectrum and 2-year outcome in a cohort of patients with very early arthritis

Objectives To describe the diagnostic spectrum, arthritis persistency and clinical outcomes after 2 years in patients with inflammatory arthritis (IA) of less than 16 weeks' duration. Methods Data from the Norwegian Very Early Arthritis Clinic, a 2-year longitudinal observational study of adults with IA of ≤16 weeks' duration, were used. Exclusion criteria were arthritis due to crystal deposits, trauma, osteoarthritis and septic arthritis. In all patients who had any follow-up information (population A), clinical diagnoses and persistency of arthritis were described. For patients with 2-year follow-up (population B), we also studied other clinical outcomes (disease activity, pain, fatigue, functional disability and health-related quality of life). Results In population A (n=1017) median (25th-75th percentile) duration of joint swelling was 35.0 (13.0-66.5) days, mean (SD) age 45.7 (14.8) years, 55.2% were females and 17.8% anticitrullinated protein antibodies positive. The most common final diagnoses were undifferentiated arthritis (UA) (41.7%), rheumatoid arthritis (RA) (24.1%) and reactive arthritis (18.1%). After 2 years, the arthritis had resolved in 59% of the patients. The remaining 41.0% had persistent disease defined by disease modifying antirheumatic drug (DMARD) use (32.1%) or persistent joint swelling without DMARD use (8.9%). In population B (n=669), all clinical outcomes improved significantly (P<0.001). Baseline joint pain and fatigue were similar across diagnoses. Conclusions Among 1017 patients with IA of ≤16 weeks' duration, UA was the most common diagnosis after 2 years, and less than one-fourth were diagnosed with RA. Arthritis resolved without DMARDs in the majority of the patients. All clinical parameters improved significantly over a 2-year course.