Abstract
Purpose The immunologic domain of the 2019 EULAR/ACR classification criteria for Systemic Lupus Erythematosus (SLE) includes the presence of anti-Sm and anti-dsDNA autoantibodies as well as low complement (C3 and/or C4) levels. Anti-dsDNA, anti-Sm and anti-Ribo-P autoantibodies are highly specific for SLE and depending on the assay used can correlate with disease activity. Low C3 and C4 levels have been associated with renal involvement and disease activity. The aim of the present study was to evaluate the association of anti-dsDNA, anti-Sm and anti-Ribo-P autoantibodies determined on a particle-based multi-analyte technology (PMAT) platform with disease activity measured by SLEDAI (SLE Disease Activity Index) score or cSLEDAI (clinical SLE Disease Activity Index) and C3 and C4 levels in a Spanish SLE cohort.
Methods A total of 197 SLE patients were tested for anti-dsDNA, anti-Sm and anti-Ribo-P autoantibodies by the novel PMAT system using the Aptiva CTD Essential Reagent (research use only) (Inova Diagnostics, USA). The correlation between anti-dsDNA, anti-Sm and anti-Ribo-P autoantibodies and SLEDAI/cSLEDAI scores, as well as between anti-dsDNA autoantibodies and complement levels were assessed by Spearman´s correlation analysis.
Results Of the 197 SLE samples, 41.6% (n=82) were single positive for each of the autoantibodies evaluated: 37.6% (n=74) were positive for anti-dsDNA, 2% (n=4) were positive for anti-Sm, and 2% (n=4) were positive for anti-Ribo-P. In addition, 4.1% (n=8) were positive for all three analytes and 7.6% (n=15) were positive for a combination of two analytes (Figure 1).
Anti-dsDNA autoantibodies determined by Aptiva-PMAT showed a positive strong correlation with disease activity (p<0.0001) and moderate negative correlation with C3 and C4 levels (p<0.0001). Anti- Sm and anti-Ribo-P showed a positive weak correlation with disease activity (p<0.0001 and p=0.0002, respectively) and negative weak correlation with C3 and C4 levels (Table 1).
Conclusion Our study shows a positive strong association between anti-dsDNA antibodies measured by Aptiva-PMATand disease activity and a moderate negative correlation with complement levels (C3 or C4).