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Volume 2011 (2011), Article ID 741071, 7 pages
Research Article

Rheumatoid Factor and Its Interference with Cytokine Measurements: Problems and Solutions

1The Parker Institute, Frederiksberg Hospital, 2000 Frederiksberg, Denmark
2Faculty of Health Science, University of Copenhagen, 2200 Copenhagen N, Denmark
3Centre for Sensory-Motor Interaction, Aalborg University, 9220 Aalborg, Denmark

Received 4 November 2010; Revised 1 April 2011; Accepted 27 April 2011

Academic Editor: Shigeru Kotake

Copyright © 2011 Else Marie Bartels et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Use of cytokines as biomarkers for disease is getting more widespread. Cytokines are conveniently determined by immunoassay, but interference from present antibodies is known to cause problems. In rheumatoid arthritis (RA), interference of rheumatoid factor (RF) may be problematic. RF covers a group of autoantibodies from immunoglobulin subclasses and is present in 65–80% of RA patients. Partly removal of RF is possible by precipitation. This study aims at determining the effects of presence of RF in blood and synovial fluid on cytokine measurements in samples from RA patients and finding possible solutions for recognized problems. IL-1β, IL-4, IL-6, and IL-8 were determined with multiplex immunoassays (MIA) in samples from RA patients prior to and after polyethylene glycol (PEG 6000) precipitation. Presence of RF does interfere with MIA. PEG 6000 precipitation abolishes this RF interference. We recommend PEG precipitation for all immunoassay measurements of plasma samples from RA patients.