Background Seropositive and seronegative rheumatoid arthritides (RA) have been considered as two different clinical entities, and traditionally autoantibodies have been associated to worse prognosis.
Objectives To assess differences in disease characteristics, presence of erosions and outcome between anti-citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF)-IgM and -IgA seropositive and seronegative early rheumatoid arthritis (ERA) patients.
Methods A total of 386 ERA patients with a disease duration of less than 12 months were enrolled in the study. Seronegative ERA patients were defined as those negative for ACPA, RF-IgM and -IgA [113 (29.3%)]; all the other subjects were defined as seropositive [273 (70.7%)]. ERA patients fulfilled the 2010 ACR criteria for RA and were followed according to the treat-to-target strategy. Subjects with symptom duration less than 3 months were defined as having “very early RA” (VERA). At baseline, and every three months, the ACR/EULAR core data set [erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), swollen joint count (SJC), tender joint count (TJC), physician and patient global assessment, pain, health assessment questionnaire (HAQ)] were recorded. At each visit, clinical improvement and remission were evaluated according to EULAR criteria.
Results At diagnosis, seronegative patients were older (p=0.002) and had shorter disease duration, comprising a greater number of VERA (p=0.04), compared to seropositive ones, and at baseline had higher average of SJC (p<0.0001), TJC (p=0.004) and consequently DAS28 (p=0.02), CDAI (p=0.001) and SDAI (p=0.001). There were no differences in gender and presence of erosion between the two analyzed cohorts. Similar percentages of good-EULAR response and DAS-remission were seen over time between seropositive and seronegative patients. Dividing patients according to the positive autoantibody, between ACPA seropositive and seronegative subjects we observed the same previously reported differences. RF-IgM and RF-IgA seropositive patients had higher ESR value (p=0.03) and were more smokers (p=0.03), compared to seronegative ones. Moreover, a higher percentage of RF-IgA seropositive patients had erosions at baseline (p=0.03), a longer disease duration (p=0.03) and BMI>30 (p=0.02), compared to seronegative subjects. At 12th month of follow-up, patients that developed new erosions or had a worsening of Sharp erosion score (13.1%, of which 6.9% were seronegative and 20.0% were seropositive, p=0.02), differed from non erosive subjects only for ACPA seropositivity (p=0.04). At the multivariate analysis, RF-IgA seropositivity [OR (95%CI): 2.25 (1.32-3.82)] and age at diagnosis [OR (95%CI): 1.02 (1.01-1.04)] arose as significant predictors of erosive disease at baseline. At 12th month of follow-up, ACPA seropositivity [OR (95%CI): 3.61 (1.38-9.45)] and age at diagnosis [OR (95%CI): 1.03 (1.01-1.06)] were the variables significantly associated to development of new erosions and to worsening of Sharp erosion score.
Conclusions Even though seronegative early RA had higher disease activity scores at diagnosis, the presence of RF-IgA and ACPA represent the strongest risk factors for being erosive and developing new erosions.
Disclosure of Interest None declared