Enzyme Immunoassay for the Detection of RF (IgM to IgG) in Human Serum.

Rheumatoid arthritis (RA) is an inflammatory disease of unknown etiology characterized by chronic proliferation of the joint cartilage. An important clinical feature of this disease is the occurrence of rheumatoid factors (RF) in the blood or synovial fluid of the patient. RF are immunoglobulins of IgA, IgM, or IgG isotypes directed against the Fc portion of IgG. Such immunoglobulins are present in approximately 4% of all individuals, although only 2% of the general population suffer from RA. The reason is that RF are also produced in response to non-RA-related immune challenges such as viral infections. Yet RF occurs in significantly higher titers in RA patients than in those possessing these factors due to of other diseases. The predominant circulating rheumatoid factor in RA is IgM, and hence; most RF detection methods aim at quantitating this immunoglobulin. The MDI RF Test is an enzyme-linked immunosorbent assay intended for the semi - quantitation of IgM antibodies against IgG, which in comparison to other conventional methods such as sheep cell agglutination or latex fixation, has the advantages of short incubations, increased sensitivity, and specificity.

SUMMARY OF 510 (k)

MDI RF Test reagents (P/N: RFKi-G) are intended for the semi-quantitative determination of IgM antibodies to IgG in human serum. The principal diagnostic value of this test is detection of autoantibodies, which are used as an aid in patients with rheumatoid diseases. The Micro Detect, Inc. RF reagent ( MDI RF Test) is intended to be used as a manual procedure. The reagents are supplied as a micro plate coated with specific antigens and Controls, Wash Buffer, Sample Diluent, Conjugate, Substrate, and Stop Solution. The patient results obtained using the MDI RF Test is substantially equivalent to those obtained by using predicate assays:

Relative Sensitivity: 95.2%

Relative Specificity:100 %

Precision (%CV): 1.9 - 5.15(Inter) and 1.44 - 3.62(Intra)

Stability: One year at 2-8 C. The stability of the MDI RF Test Kit for the detection of IgM antibodies to IgG was found to be one year at 2-8 C. This was predicted from studies done under stress condition (47.5 C). Real time stability has only been monitored for ten weeks at 2-8 C.

The MDI RF Test system is shown to be safe and effective and provide results, which are substantially equivalent to those, obtained by predicate products.