THU0345 Sensitivity and specificity of antibodies against carbamylated proteins in a monocentric cohort of patients with systemic lupus eritamatosus and rheumatoid arthritis
Authors: B. Özdemir, O. Kucuksahin, T.H. Yeşil, S. Akan, S. Erten
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterised by numerous organ involvement. In SLE, autoantibody development against nucleic acids and their binding proteins plays an important role in disease pathogenesis. <h3>Objectives</h3> Purpose of this study is the determination of the diagnostic value of anti-carbamyl antibody in patients with Systemic Lupus Erythematosus and rheumatoid arthritis and the relationship with disease prognosis. <h3>Methods</h3> Fifty-seven SLE patients (F/M 50/7; median age 40.9±13.7; median disease duration 2 years) were included in the study according to the 2012 SLICC SLE diagnostic criteria. 46 RA patients (F/M 38/8, median age 54.2±12.4 years, the median duration of disease 2 years) selected according to 2010 ACR/EULAR diagnostic criteria were included. 30 healthy control groups were selected. Anti carP antibody Anti-carbamylated Protein Human anti-carbamylated Protein Antibody (ACP-Ab) ELISA Kit (SunRedBio, China) was used for measurement of antibodies against carbamylated proteins. <h3>Results</h3> The study population consisted of 133 subjects, 30 controls, 57 SLEs and 46 RAs. The mean age of SLE patients was lower than that of RA patients. (40,9±13,7 versus 54,2±12,4; p&lt;0,001). The proportion of active smokers was found to be higher in RA patients compared to SLE patients (19.6% versus 5.3%, p=0.005). The frequency of anti carP antibody positivity was 3.3% in the healthy control group. In contrast, the frequency of anti carP antibody positivity was found as high as 17.4% in patients with RA. (p=&lt;0.001), And this frequency was 54.4% in the SLE patient group (p=&lt;0.001) Anti carP antibody predicted SLE patients with 54.4% sensitivity and 96.7% specificity compared to the healthy control group. (AUC: 0.755, p&lt;0.001) Anti carP antibody predicted RA patients with 17.4% sensitivity and 96.7% specificity compared to the healthy control group (AUC: 0.570, p=0.032). Anti carP antibody predicted SLE patients with 54.5% sensitivity and 82.6% specificity compared to healthy RA group (AUC: 0.685, p&lt;0.001). AnticarP antibodies were found to be positive in all of the SLE patient groups with anti-CCP positivity. There was no significant difference in terms of in organ involvement between anti-carp antibody positive or negative SLE patients. Anti-carP antibody positivity was assessed by ROC Curve analysis for the prediction of diagnostic performance in SLE patients compared to RA patients. Accordingly, Anti carP antibody positivity, ANA positivity, were found to have similar diagnostic performance. (AUC: 0.639) <h3>Conclusions</h3> Antibody positivity was found to be 54.4% in SLE patient group. It is significantly higher in SLE compared to healthy control and RA patient group. In the SLE group, it is still a more significant diagnostic prognostic than the healthy control and RA group. Both SLE and RA patients have significant sensitivity and specificity compared to the healthy control group. <h3>Disclosure of Interest</h3> None declared