Background In patients with inflammatory arthritis, the autoantibodies rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) have been associated with poor outcomes such as increased disease activity, radiographic progression and disability. However, the utility of antibody level in predicting prognosis of inflammatory arthritis, in particular rheumatoid arthritis (RA), has not clearly been established.
Objectives To investigate RF and ACPA status and levels as predictors of mortality in two large cohorts of patients with early inflammatory arthritis (EIA).
Methods Data from the Norfolk Arthritis Register (NOAR) and Leiden Early Arthritis Clinic (EAC) cohort were used. At baseline, patients had demographic data and smoking status recorded; RF, ACPA and inflammatory markers were measured in the local laboratories. Patients were flagged with national death registers until death or censor date. Antibody status was stratified as negative, low or high positive as defined in the 2010 criteria, firstly by either RF or ACPA level, secondly by RF level alone and thirdly by ACPA level alone. Finally, patients were grouped as seronegative, single antibody positive or double antibody (RF and ACPA) positive. Cox regression models were applied to explore associations between antibody status and mortality adjusting for age, sex, smoking status, inflammatory markers and year of enrolment.
Results 4962 (NOAR: 3053, EAC: 1909) patients were included. 35% and 42% of patients were ACPA/RF positive in NOAR and EAC respectively. There were 787 deaths during 36 109 person years follow up in NOAR, and 275 deaths during 16 187 person years follow up in the EAC. When antibody status was stratified as negative, low or high positive, there were no consistent findings between the two cohorts. Double antibody positivity was associated with excess mortality in both cohorts compared to seronegative patients: NOAR and EAC respective adjusted HR (95% CI): 1.35 (1.06-1.71) and 1.58 (1.16-2.15).
Conclusions Patients with EIA who are seropositive for both RF and ACPA have increased mortality compared to those who are single positive or seronegative. Antibody level in seropositive patients was not consistently associated with excess mortality.
Disclosure of Interest None declared