Antibodies against Sm are specific serological markers of systemic lupus erythematosus (SLE) while antibodies against Sm/RNP are found in several connective tissue diseases, principally SLE and MCTD. Ro (SS-A) and La (SS-B) are RNA-protein complexes and antibodies against them are found in Sjögren’s syndrome, SLE, scleroderma, and neonatal lupus erythematosus.
The DIASTAT® ENA Profile kit is a qualitative enzyme-linked immunosorbent assay (ELISA). It allows four parallel but separate tests to be performed for the detection of autoantibodies specific for Sm, Sm/RNP, Ro (SS-A) and La (SS-B) antigens in human serum or EDTA, lithium heparin, citrated plasma. It is intended to aid in the diagnosis of systemic rheumatic diseases and is not definitive in isolation. Autoantibody levels represent one parameter in a multicriterion diagnostic process.
Systemic rheumatic diseases are autoimmune disorders such as systemic lupus erythematosus (SLE), polymyositis, Sjögren's syndrome, scleroderma and mixed connective tissue disease (MCTD). A general feature of systemic rheumatic diseases is the presence of circulating antibodies to a variety of cellular antigens. The detection and serological characterisation of specific autoantibodies plays an important role in the differential diagnosis of these diseases. Determining the autoantibody profile gives maximum diagnostic value, therefore it is recommended that patient samples are screened for each autoantibody. Separate kits, which also have a quantitative option, are available for each of the autoantibodies in this kit.
Sm is a non-histone glycoprotein; antibodies against this extractable nuclear antigen are specific serological markers of SLE.
U1-RNP is a ribonucleoprotein; antibodies against it are found in several connective tissue diseases, principally SLE (30-40%) and MCTD (>95%). MCTD presents a combination of clinical features, which may also be seen in SLE, polymyositis and scleroderma. Although antibodies to dsDNA, Sm and Ro are occasionally found in MCTD, high titres of anti-RNP antibodies are usually considered diagnostic of the disease.
Ro (SS-A) and La (SS-B) are RNA-protein complexes; antibodies against them are found in Sjögren's syndrome (60% and 40% respectively), SLE (30% and 15%), scleroderma, and neonatal lupus erythematosus. There is evidence associating these antibodies to particular clinical characteristics, and linking them with congenital heart block.
The wells of the microtitre strips are coated with one of the four affinity-purified antigens. During the first incubation, specific autoantibodies in diluted serum or plasma bind to the antigen-coated surface. The wells are then washed to remove unbound components. In the second incubation, the Conjugate, enzyme-labelled antibodies to human IgG, binds any surface-bound autoantibodies. After further washing, specific autoantibodies are traced by incubation with the Substrate. Addition of Stop Solution terminates the reaction, resulting in a coloured end-product. The amount of Conjugate bound is measured in absorbance units and compared with that bound by the appropriate Reference Control.