B-103 Correlation of Novel Markers, Anti-Sa (Citrullinated Vimentin) and Anti-CarP (Carbamylated Protein), with High Vectra® DA Disease Activity Scores in Rheumatoid Arthritis (RA)
Authors: Yang J M , Punzalan R , Nappi M , Chun K Y 
Published: October 2024

Abstract

Background
Citrullination and carbamylation are post-translational modifications where autoantibodies against citrullinated and carbamylated proteins in RA have been associated with more aggressive disease. At the same time, Vectra® DA is blood test that yields a RA disease activity score from 1 to 100. Here, 120 patient samples were analyzed to assess the relationship of disease activity as measured by Vectra® score and the presence of Anti-Sa (Citrullinated Vimentin) and Anti-CarP (Carbamylated Protein).

Methods
Serum samples were analyzed for Vectra® DA (which is validated for adults with RA) where 12 biomarker measurements (VCAM-1, EGF, VEGF-A, IL-6, TNF-RI, MMP-1, YKL-40, Leptin, Resistin, SAA, CRP) together with patient age, gender and adiposity are used to generate a score where established categories are low for 1 to 29, moderate for 30 to 44, and high for 45 to 100. Anti-Sa and Anti-CarP were by ELISA lab-developed tests (LDT) with a cut-off for positive of &gt;20 Units (U).

Results
Anti-Sa and Anti-CarP for 40 samples from each Vectra® DA category are reported. Patients with the highest Vectra® scores (mean 58.2, range 46.8 - 87.5) had highest rates of positivity for Anti-Sa (52.5%) and Anti-CarP (35%). In contrast, the group with the lowest Vectra® scores (mean 11.8, range 3.8 - 18.1) were infrequently positive for Anti-Sa (17.5%) and Anti-CarP (0%). Frequencies with moderate Vectra® scores (mean 37.1, range 32.4 - 41.8) were mid-range: Anti-Sa (25%) and 7.5% for Anti-CarP (7.5%). Of note, positivity of Anti-Sa was analytically stronger, i.e. higher titer, in patients with moderate or high Vectra® (mean 90.0U or 81.7U), compared to values seen in those with low Vectra® (mean 60.4 U).

Conclusions
Our analysis of 120 patient samples demonstrates that high disease activity as determined by Vectra® DA corresponds to higher positivity of novel autoantibody markers, Anti-Sa and Anti-CarP. High Vectra® DA scores (&gt;44) are associated with a 20% 1-year risk of radiographic progression while low scores (&lt;30) carry only a 1% risk. Here, we found that patients with high Vectra® scores were 3 times more likely to test positive for Anti-Sa than those with low disease activity scores. At the same time, Anti-CarP occurred in high frequency (35%) with high Vectra® in contrast to zero positivity observed with low Vectra® scores. Thus, our findings support Anti-CarP’s reported association with more active disease with higher risk of developing joint erosions. Also of note, patients with high Vectra® scores had particularly high Anti-Sa positivity - both a 52.5% positivity rate as well as higher Anti-Sa levels (titers) than the group with lower Vectra® scores. These data corroborate other studies where Anti-Sa not only predicted more aggressive, rapid disease progression, but its titers correlated with clinical measures of disease activity. Taken together, our data support the consistency and clinical usefulness of the Vectra® score along with novel autoantibody markers, Anti- Anti-Sa and Anti-CarP, in order to assess RA severity, prognosis, and patient-specific treatment strategies.