To investigate anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF) in relation to ultrasound-detected joint inflammation and bone erosion in patients with rheumatoid arthritis (RA) as previous studies have mainly utilized radiographic damage as imaging outcomes.
In this cross-sectional study, patients were grouped based on their Disease Activity Score at 28 joints (DAS28 < 3.2, DAS28 ≥ 3.2). Ultrasound variables (power Doppler and gray scale joint inflammation graded 0-3 semi-quantitatively; bone erosion graded Yes = 1/No = 0 dichotomously) were correlated with antibodies levels using Pearson correlation. Simple linear regression was used to characterize relationships between variables. Receiver operating characteristic (ROC) analysis was performed to determine statistically optimal cut-off values for identifying patient subgroups with ultrasound erosion scores >25th, >50th and >75th percentiles.
One thousand and eighty joints and 1800 joint recesses from 36 peripheral joint sites were scanned in 30 adult RA patients (mean disease duration, 70.3 months; 93.3% female; 93.3% anti-CCP positive; 93.3% RF positive). In the DAS28 < 3.2 group, no significant correlations were found between antibody levels and ultrasound variables. In the DAS28 ≥ 3.2 group, anti-CCP levels correlated significantly (r = 0.46, P = .048) and were predictive (P = .048) of ultrasound erosion scores. Area under the ROC curve based on cut-off anti-CCP level of ≥95.2 to identify patients with ultrasound erosion scores >7 (75th percentile) was 0.72 (sensitivity = 83.3%, specificity = 53.8%).
The association of anti-CCP and RF with joint damage appears to differ in RA. Among patients with at least moderate disease activity (DAS28 ≥ 3.2), anti-CCP-but not RF-is associated with joint damage, being moderately correlated with ultrasound-detected bone erosion.