Rheumatoid factor isotypes, disease activity and the outcome of rheumatoid arthritis: Comparative effects of different antigens

Abstract

The value of rheumatoid factor (RF) isotypes for assessing rheumatoid arthritis (RA) remains debatable. We investigated whether using different antigens to measure RF alters the relationships between RF isotypes and clinical variables. The association between IgA and IgM RF, disease activity, and cumulative anatomical joint damage in RA was studied in 140 patients. The RF isotypes were measured using both rabbit IgG and horse IgG as antigens. Cumulative anatomical damage was assessed radiologically using Larsen's score and disease activity was determined by C-reactive protein (CRP), the health assessment questionnaire (HAQ), and a combined disease activity score (DAS). Patients positive for IgA RF and IgM RF against rabbit IgG had significantly higher disease activity and more radiological damage than negative patients. With horse IgG as antigen these differences were smaller or absent. Patients positive for only IgM RF had milder disease than patients positive for IgA RF with or without IgM RF. The clinical relationships of RF isotypes are related to the antigen used. Measuring IgA RF against rabbit IgG provides most information about disease activity, functional impairment and joint damage.

The Contribution of Four Immunogenetic Markers for Predicting Persistent Activity in Patients with Recent-Onset Rheumatoid Arthritis or Undifferentiated Arthritis

“…Had we used a cutoff value of ≥40 IU/mL, the frequency of RF positivity would have been 58.7%, instead of 42.3%. Several studies have reported that RF is a good predictor of disease activity [23, 24, 26–31]. However, in our univariate analyses RF, treated either as a qualitative or a quantitative variable, was not significantly associated with DAS28 (Table 2).…”

Clinical, Immunological and Inflammatory Characteristics among Mexican Children with Different Subtypes of Juvenile Idiopathic Arthritis: Exploring the Correlation between Anti-Cyclic Citrullinated Peptide (anti-CCP) and Rheumatoid Factor (RF)

“…The diagnosis of JIA is made clinically, although there are some biochemical markers that have a certain utility both in the classification of JIA and in its association with extraarticular manifestations. One of these markers is RF, which is found in adult patients with rheumatoid arthritis (RA), but in pediatric patients, its absence does not rule out the disease; therefore, this marker is not useful for diagnosis, although it is useful for the classification of JIA under the ILAR criteria [4][5][6][7]. Another marker is antinuclear antibodies (ANAs), whose presence is associated with the risk of uveitis.…”