Background/Purpose:

Concomitant presence of anti-cyclic citrullinated peptide antibodies (ACPA) and rheumatoid factor (RF) is associated with higher erosive disease burden in patients with established rheumatoid arthritis (RA). Even before the clinical onset of arthritis, ACPAs are associated with bone loss. Whether RF also influences bone damage in patients with RA is less well defined. In this study, we aim to determine whether there is an effect of ACPA and RF on the number and volume of bone erosions in early rheumatoid arthritis (ERA) patients.

Methods:

In this cross-sectional study, the second metacarpophalangeal joint (MCP2) in 96 patients with ERA (onset of disease within 2 years) were assessed using high-resolution peripheral quantitative CT (HR-pQCT). Data on demographic (age, sex) and disease-specific parameters including DAS 28, ESR, CRP, ACPA and RF levels were recorded. Erosions were visualized in 73 patients and the number and volume of the erosions were documented. Relationship between erosions, demographic and disease-specific data was evaluated by two multiple linear regression models.

Results:

Amongst the 96 ERA patients, 72.9% were female. The mean age was 53.1±13.8 years, disease duration was 8.0±5.6 months and DAS 28 was 5.0 ±0.9. Out of the 96 patients, 75 were both RF and ACPA positive (ACPA+/RF+), 5 were RF positive only (ACPA-/RF+), 9 were ACPA positive only (ACPA+/RF-) and 7 were double negative (ACPA-/RF-). Erosion volume was higher in the ACPA+/RF+ group compared with the non- ACPA+/RF+ (ACPA-/RF+ or ACPA+/RF- or ACPA-/RF-) group (3.99±3.16 mm³ vs 2.50±1.24 mm³, p=0.023). When all patients were subdivided according to RF and ACPA titer, erosion volume was significantly larger in the RF positive (>16 U) group than the RF negative (<16 U) group (4.28±3.42 mm³ vs 2.66±1.34 mm³, p=0.019). Similarly, erosion volume was also significantly larger in the ACPA>100U group compared to the ACPA<100U group (2.94±3.19 mm³ vs 1.64±1.34 mm³, p=0.010). Erosion volume was also increased in female patients (Beta=0.315, p=0.012). On the other hand, erosion number was associated with increasing age (Beta=0.359, p=0.000), ESR (Beta=0.320, p=0.001) and longer disease duration (Beta=0.251, p=0.014) in the univariate analysis. Using multiple linear regression model, independent explanatory variables associated with erosion volume included RF>16U (p=0.018) and female gender (p=0.011); while erosion number was associated with a longer disease duration (p=0.021), older age (p=0.000) and elevated ESR (p=0.007).

Conclusion:

In RA patients with recent onset of disease, the number of erosion appears to depend on disease activity, while the presence of RF may play a predominant role in the structural deterioration in terms of erosion volume. .