Enriching case selection for imminent RA: the use of anti-CCP antibodies in individuals with new non-specific musculoskeletal symptoms - a cohort study.

Abstract

Around 1% of the population test positive for anti-cyclic citrullinated peptide (anti-CCP) antibodies. This biomarker predicts the progression to rheumatoid arthritis (RA) but over a variable time frame. To increase its clinical relevance, this study sought to determine (1) if the proportion of anti-CCP-positive individuals could be enriched by case selection of people attending primary care with new non-specific musculoskeletal (MSK) symptoms but without clinical synovitis (CS) and (2) whether these individuals progress rapidly to inflammatory arthritis (IA), in particular RA. In this prospective cohort study, individuals aged ≥18 years with new non-specific MSK symptoms, without CS, were recruited from primary care in the UK. Anti-CCP-positive individuals were invited for follow-up in the rheumatology department, Leeds. Those who tested negative were sent questionnaires 12 months later. 2028 individuals were recruited. Of these, 2.8% (57/2028) were anti-CCP positive, of whom 47% (27/57) developed IA - 24 RA, 1 undifferentiated IA (UIA), 2 polymyositis; 92.6% (25/27) within 12 months, median 1.8 months (IQR 1.0-4.3, range 0.3-16.1). Of the anti-CCP-negative individuals, 1.3% (20/1559) developed IA (1 UIA, 13 RA, 6 psoriatic arthritis); 75% (15/20) within 12 months. The relative risk for developing RA within 12 months in the anti-CCP-positive group was 66.8 (95% CI 32.2 to 138.4, p<0.001); for IA, it was 45.5 (95% CI 25.4 to 81.6, p<0.001). Selecting individuals with new non-specific MSK symptoms without CS enriched the prevalence of anti-CCP positivity to 2.8%. Those who tested positive had a high risk of rapidly developing RA. The cost-effectiveness of this approach will need to be determined. NCT02012764.