Background

Detection and serological characterisation of specific autoantibodies play an important role in the differential diagnosis of systemic rheumatic diseases. Autoantibodies to nuclear antigens (ANAs) are a group of antibodies specific for nuclear antigens including Sm, Sm/RNP, Ro (SS-A), La (SS-B), Scl-70, Jo-1, dsDNA, histone and centromere antigens. A positive ANA test result provides presumptive evidence for systemic rheumatic disease and further definition of specific antibody profiles is a valuable aid in the diagnostic process. A negative result reduces, but does not exclude, the likelihood of systemic rheumatic disease.
 

Technical information

The wells of the microtitre strips are coated with highly purified HEp-2 cell extract. During the first incubation, specific ANAs in diluted serum or EDTA 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 and IgM, 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 Reference Control.