Enzyme Immunoassay for the Detection of autoantibodies to Sm/RNP in Human Serum.

Autoimmunity is characterized by the presence of antinuclear antibodies (ANA) against nuclear macromolecules. Specific combinations of circulating ANA are diagnostic of the different types of autoimmune diseases. Therefore, identification of specific autoantibodies is important in the identification and treatment of the autoimmune diseases.

TThe Smith (Sm) antigen and small nuclear ribonucleoproteins (snRNP) are RNA-protein complexes responsible for the processing of mRNA. This group of non-histone nuclear antigens is comprised of U1, U2, U4, U5, and U6 complexes of which the polypeptides associated with the U1 complex constitute the majority of the snRNP antigens. Antibodies to Sm are solely found in the sera of systemic lupus erythematosus (SLE) patients and serve as specific markers of that disease. On the other hand, anti-snRNP antibodies have been correlated with a variety of diseases such as Sjogren's Syndrome, Progressive Systemic Sclerosis, rheumatoid arthritis, Drug Induced Lupus, and Mixed Connective Tissue Disease (MCTD). In most cases, the presence of anti-snRNP antibodies alone is indicative of MCTD.

Until recently, hemagglutination, counterimmunoelectrophoresis, and immuno-diffusion have been the predominant methods of choice for the detection of anti-Sm/RNP antibodies; however, these techniques are labor-intensive and time-consuming. Comparative studies have shown that enzyme immunoassays are more reliable in the detection of serum antibodies to Sm and snRNP.

SUMMARY OF 510 (k)

MDI Sm/RNP Test reagents (P/N: RNKi-G) are intended for the semi quantitative determination of IgG antibodies to Sm/RNP 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. Sm/RNP reagent ( MDI Sm/RNP 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 Sm/RNP Test is substantially equivalent to those obtained by using predicate assays:

Relative Sensitivity: 96.2%

Relative Specificity:97.9 %

Precision: 2.29-5.59(Inter) and 2.07-7.01(Intra)

Stability: One year at 2-8 C. The stability of the MDI Sm/RNP Test Kit for the detection of IgG antibodies to Sm/RNP was found to be one year at 2-8 C. This was predicted from studies done under stress condition (37 C). Real time stability is being monitored at 2-8 C.

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