Human IgM Rheumatoid Factor ELISA Kit (in USA-for in vitro research use only-not for use in diagnostics) Manufactured by CLB Reagents (Netherlands Red Cross)

CAT#: RDI-M1950clb PRICE: $250.00/kit

Introduction:

In serum of patients with rheumatoid arthritis (RA), commonly rheumatoid factors (RF) can be detected. RF are antibodies directed to the Fc part of antibodies of the human IgG class. In most cases RF belong to the IgM class (IgM-RF), occasionally RF of the IgG class (IgG-RF) can be found together with IgM-RF.At variance, rarely sera with circulating IgG-RF and no IgM-RF were found. Close examination of sera from RA patients and healthy individuals demonstrated equal frequencies of the occurrence of IgG-RF in both populations.Consequently, it was concluded that the quantification of IgG-RF did not improve the serological diagnosis of RA.

Numerous methods for the measurement of RF have been used; the majority of routine laboratory tests have been based on the ability of RF to agglutinate latex,bentonite,human and sheep red blood cells and other carrier particles coated with immunoglobulin. These tests are semi-quantitative, and in order to achieve accurate RF quantification, sensitivity and specificity, several other tests have been developed. These include radioactive immunoassay, nephelometric assay and the enzyme linked immunoassay (ELISA). From these tests, the ELISA was found to be the most sensitive method for the determination of IgM-RF in serum. Furthermore the IgM-RF ELISA data can be better quantified as compared to agglutination methods.

In most healthy individuals IgM-RF values < 12.5 U/ml were found.

Kit Contents:

Precoated microtiterplate (12 strips, 96 wells)

Lyophilized standard (calibrated against Dutch national and WHO standard) and controls

HRP-conjugated anti-IgM-RF antibody

Wash-,incubation-,and substrate-buffers

Characteristics:

Sensitivity: 0.7U/ml (Mean Blank signal + 3 sd),

1.0U/ml (2 x Blank signal)

Intra-assay variation: < 4%

Intra-assay variation: < 8%

Total assay incubation time: 2h 30min

Standard curve: 0.031 - 2 U/ml

Applications:

Testing for IgM-RF has a high diagnostic value, as their detection or exclusion can support or place doubt on a tentative diagnosis based on case history data and clinical findings. Since there is substantial evidence indicating a role of IgM-RF in the pathogenesis of RA and the formation of complement activating immune complexes,a seropositive IgM-RF generally has a more unfavorable prognosis than the seronegative form. IgM-RF can be detected not only in RA but also in a number of other connective tissue diseases, therefore the results of IgM-RF determination should always be assessed in connection with clinical and other laboratory findings.

References:

Adebajo,A.O.et al (1992)Scand.J.Rheumatol.21:302

Dorner,R.W.et al (1987) Clin.Chim.Acta 167:1

Harris,E.D.(1990) N.Engl.J.Med. 322: 1277

Klein,F.et al (1987) Ann.Rheum.Dis. 46:674

Mannik,M.(1992) J.Rheumatol.19:46

RF review issue(1988) Scand.J.Rheumatol.75:1

Rheins,M.S.et al (1957) J.Lab.Clin.Med.50:113

Rose,H.M.et al(1948)Proc.Soc.Exp.Biol.Med.68:1

Silman,A.J.(1987) Br.J.Rheumatol. 27:342

Singer,J.M.et al(1956) Am.J.Med. 21:888

Vademecum diagnostisch onderzoek CLB (1993):137

Waaler,E.(1940) Acta Pathol.Micribiol.Scand.17:172

Williams,R.C.(1992) J.Rheumatol. 19:42

Assay procedure:

-Bring all reagents to room temperature Wash 4 times

-Incubate 100 ul of standards,controls and samples (1 hour 37'C) Wash 4 times

-Incubate with 100 ul of HRP-conjugated anti-IgM-RF antibody (1hour 37'C) Wash 4 times

-Incubate with 100 ul substrate solution (30 min,room temperature, in the dark)

-Add 50 ul stop solution

-Read absorbance at 414 nm.