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Introduction Rheumatoid factors (RFs) are autoantibodies that bind to epitopes within the constant region (Fc) of IgG. The first evidence for their existence was found in 1937 when sera from patients with rheumatoid arthritis (RA) were shown to cause agglutination of sheep red blood cells opsonized with rabbit IgG (rIgG) [ 1 ], [ 2 ]. Presently, both RF status and level are part of the classification criteria for RA [ 3 ], and while the more recently discovered anti-citrullinated protein antibodies (ACPAs) have a higher specificity for RA [ 4 ], [ 5 ], RFs are

Clin Chem Lab Med 2011;49(5):873–875 2011 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2011.144 2010/563 Article in press - uncorrected proof Short Communication Thyroxin overdose due to rheumatoid factor interferences in thyroid-stimulating hormone assays Agnès Georges1, Anne Charrié2, Sophie Raynaud3, Christine Lombard4 and Jean-Benoı̂t Corcuff1,* 1 Department of Nuclear Medicine, University Hospital and University Bordeaux, Pessac, France 2 Department of Biology-Endocrinology-Nutrition- Metabolism, Hospices Civils de Lyon and University Lyon

1 Introduction Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint swelling, joint tenderness and destruction of synovial joints, leading to severe disability and premature mortality. The disease affects 1% of population worldwide [ 1 ]. Given the presence of autoantibodies such as rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA), which can precede the clinical manifestation of RA by many years, RA is considered an autoimmune disease [ 2 ]. Early diagnosis of the disease is of crucial importance, as precocious

Clin Chem Lab Med 2009;47(8):959–962 2009 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2009.217 2009/83 Article in press - uncorrected proof Anti-citrullinated protein antibody and rheumatoid factor in patients with end-stage renal disease Zeljko Romic1, Adriana Unic1,*, Lovorka Derek1, Marcela Zivkovic1, Domagoj Marijancevic1, Petar Kes2 and Mario Pehar3 1 Clinical Department for Laboratory Diagnostic, Dubrava University Hospital, Zagreb, Croatia 2 Department of Dialysis, University Hospital Center Zagreb, Zagreb, Croatia 3 Department of Dialysis

without autoimmune disease. Clin Exp Immunol 2001;126:540--4. Jónsson T, Thorsteinsson J, Valdimarsson H. Does smoking stimulate rheumatoid factor production in non-rheumatic individuals? Acta Pathol Microbiol Immunol Scand 1998;106:970--4.

References 1. Alpert JS, Thygensen K, Antman E, Bassand JP, Klein W, Ohman M, et al. Myocardial infraction redefined – a consensus of the Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infraction. J Am Coll Cardiol 3000; 36:959–69. 2. Krahn J, Parry D, Leroux M, Dalton J. High percentage of false positive cardiac troponin I results in patients with rheumatoid factor. Clin Biochem 1999; 32:477–80. 3. Katwa G, Komatireddy G, Walker SE. False positive elevation of cardiac troponin I in seropositive

is seen with this strategy in reducing joint destruction, retarding radiologic progression and decreasing functional disability [ 4 ]. Anti-citrullinated peptide antibodies (ACPAs) and rheumatoid factor (RF) belong to the serum biomarkers involved in the 2010 American College of Rheumatology (ACR)/the European League Against Rheumatism (EULAR) RA classification criteria, no doubt underscoring the serodiagnostic utility of these autoantibodies in RA. Furthermore, ACPAs include anti-cyclic citrullinated peptide (anti-CCP), anti-mutated citrullinated vimentin (anti

Jaspers et a!.: Nine rheumatoid factor assays compared 863 J. Clin. Chem. Clin. Biochem. Vol. 26, 1988, pp. 863-871 © 1988 Walter de Gruyter & Co. Berlin · New York Nine Rheumatoid Factor Assays Compared By J. P. M. M. Jaspers Department of Clinical Chemistry, Het Nieuwe Spinaal, Warnsveld, The Netherlands R. J. M. Van Oers and B. Leerkes Department of Clinical Chemistry, Ziekenhuiscentrum Apeldoorn, Juliana Ziekenhuis, Apeldoorn, The Nether- lands (Received April 18/October 3, 1988) Summary: In this study we have investigated five quantitative and three semi

Abstract

Background: Investigation of a 61-year-old Caucasian male suffering from fatigue and weight loss led to the finding of a carbohydrate antigen 19-9 (CA 19-9) concentration of 80kU/L using an ADVIA Centaur analyser. Determination of CA 19-9 on Vidas, AxSYM and Architect i2000 systems gave normal results. His rheumatoid factor concentration was very high (900kIU/L) and assay interference was suspected.

Methods: Besides using several laboratory procedures to show the cause of the interference, we tried to estimate the frequency of the suspected interference. Therefore, two studies were performed. The first was carried out in a multicentre setting using four different CA 19-9 methods on 51 randomly selected samples with high rheumatoid factor concentrations and ten samples containing no or very low rheumatoid factor. In the second study we used heterophilic blocking tubes for 68 routinely analysed samples with CA 19-9 concentrations ranging between 37 and 250kU/L using an ADVIA Centaur analyser.

Results: In the multicentre study we found eight discrepant CA 19-9 results, but only one was clearly due to interference. We showed that the interference detected, just as in the index case, was caused by rheumatoid factor. The other discrepancies could not be explained, but are probably related to method-dependent differences. In the 68 routinely analysed samples, no interference could be shown using the heterophilic blocking tubes.

Conclusions: Although interferences in the CA 19-9 assay are not frequent, the ADVIA Centaur system appears to be more sensitive to rheumatoid factor interference. The lack of standardisation remains an important issue for this assay. The determination of CA 19-9 during the follow-up of patients should be performed using a single method. If, however, there is any clinical doubt about a result, CA 19-9 should be determined using another method to exclude possible interferences.

Clin Chem Lab Med 2006;44:1137–9.

Clin Chem Lab Med 2009;47(1):116–117 2009 by Walter de Gruyter • Berlin • New York. DOI 10.1515/CCLM.2009.020 2007/298 Article in press - uncorrected proof Letter to the Editor Falsely elevated carbohydrate antigen 19-9 level due to heterophilic antibody interference but not rheumatoid factor: a case report Yan Lianga, Zaixing Yanga, Weimin Ye, Jie Yang, Mingjun He and Renqian Zhong* Department of Laboratory Diagnostics, Changzheng Hospital, Second Military Medical University, Shanghai, China Keywords: carbohydrate antigen 19-9; heterophilic antibodies