Enzyme immunoassay for the detection of autoantibodies to Scl-70 in human serum.

Autoimmunity is characterized by the presence of antinuclear antibodies (ANA) against a multitude of 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 disease.

The Scl-70 antigen, also known as topoisomerase I, is a chromosome-associated nonhistone protein involved in the regulation of DNA replication. Anti-Scl-70 antibodies are highly specific for scleroderma, a disorder of arteries and microvessels. Antibodies to Scl-70 are found in approximately 25% of patients with scleroderma and some variants of that disease.

Until recently, hemagglutination, counterimmunoelectrophoresis, and immuno-diffusion have been the predominant methods of choice for the detection of anti-Scl-70 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 Scl-70. The Micro Detect anti-Scl-70 test is an enzyme-linked immunosorbent assay, which in contrast to other methods, has the advantages of short incubations, increased sensitivity, and specificity.

SUMMARY OF 510 (k) SAFETY AND EFFECTIVENESS INFORMATION

MDI Scl-70 Test reagents (P/N: ScKi-G) are intended for the semi-quantitative determination of IgG antibodies to Scl-70 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. Scl-70 reagent ( MDI Scl-70 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 Scl-70 Test is substantially equivalent to those obtained by using a predicate assay:

Relative Sensitivity: 98.4%

Relative Specificity: 96.1 %

Precision (%CV): 1.57-8.99 (Inter) and 3.73-9.50 (Intra)

Stability: One year at 2-8 C. The stability of the MDI Scl-70 Test Kit for the detection of IgG antibodies to Scl-70 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 six weeks at 2-8 C.

The MDI Scl-70 Test system is shown to be safe and effective and provide results, which are substantially equivalent to those, obtained by predicate products.