Session Information
Date: Monday, October 22, 2018
Title: Rheumatoid Arthritis – Diagnosis, Manifestations, and Outcomes Poster II: Diagnosis and Prognosis
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose:
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.
Methods:
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).
Results:
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%.
Conclusion:
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 9). https://acrabstracts.org/abstract/value-of-anti-ra33-isotypes-in-an-european-rheumatoid-arthritis-patient-cohort/. Accessed .ACR Meeting Abstracts - https://acrabstracts.org/abstract/value-of-anti-ra33-isotypes-in-an-european-rheumatoid-arthritis-patient-cohort/