Date: Monday, October 22, 2018
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Early diagnosis of rheumatoid arthritis (RA) leading to effective treatment is essential to improve prognosis and to prevent disease progression. Anti-cyclic citrullinated peptide (CCP) antibodies (ACPA) offers similar sensitivity, but higher specificity for RA than rheumatoid factor (RF) in early RA. In single analyte-testing scenarios, ACPA can detect approx. 70% of RA patients but fewer during early RA (~ 60%). As a biomarker for RA, anti-RA33 IgG antibodies are known to be specific, especially in the early stage of the disease. Recent studies show an emerging role of all three anti-RA33 isotypes in diagnosis and prognosis of RA1.
The aim of this study was to evaluate anti-RA33 isotypes IgM, IgA, and IgG for the diagnosis of early RA and to examine the added value compared to anti-CCP antibodies and RF within two independent European RA cohorts.
The first cohort provided by Medical University of Vienna, Austria, includes in total 654 patient samples, 257 RA patient samples and 357 control samples; various autoimmune (n=128), non-autoimmune diseases (n=130) and healthy individuals (n=99). To validate the data, a second patient cohort (MATURA, United Kingdom) consisting of 295 patient samples, 100 RA patient samples, 75 autoimmune, 70 non-autoimmune diseases and 50 healthy subjects was measured. Serum samples of both cohorts were analyzed for the presence of anti-RA33, anti-CCP and RF (each IgM, IgA, IgG) using the EliATM instrument platform (Phadia AB, Uppsala, Sweden).
Analyzing both cohorts, one third of RA patients were positive for at least one of the anti-RA33 isotypes, whereas anti-RA33 IgM showed the highest sensitivity (23%) followed by IgA (12%) and IgG (9%). Both cohorts revealed a specific pattern of all three anti-RA33 isotypes with a diverse distribution among RA patients and little overlap between the immunoglobulin classes. The combination of all three anti-RA33 isotypes detects 26% of the seronegative RA patients and the specificity of each isotype is ≥90%.
Anti-RA33 isotype distribution shows remarkably little overlap of IgM, IgA and IgG in European RA patient cohort. Therefore, the combination of all three anti-RA33 isotypes provides a considerable added value for the diagnosis of RA in the anti-CCP- and RF-negative group. To fully evaluate the importance of the different anti-RA33 immunoglobulin classes within the pathogenesis of RA, further investigations are required.
1 Sieghart, D; Platzer, A; Studenic, P; Alasti, F; Grundhuber, M; Swiniarski, S; Horn, T; Haslacher, H; Blüml, S Smolen, J; Steiner, G. Determination of Autoantibody Isotypes Increases the Sensitivity of Serodiagnostics in Rheumatoid Arthritis. Frontiers in Immunology; v:9 p:876; 2018
To cite this abstract in AMA style:Grundhuber M, Sieghart D, Steiner G, Poorafshar M, Swiniarski S. Value of Anti-RA33 Isotypes in an European Rheumatoid Arthritis Patient Cohort [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). https://acrabstracts.org/abstract/value-of-anti-ra33-isotypes-in-an-european-rheumatoid-arthritis-patient-cohort/. Accessed January 24, 2022.
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