Useful For

The ANA Screen detects the presence of clinically relevant circulating autoantibodies in serum or plasma. These autoantibodies may be useful as an aid in the diagnosis of systemic autoimmune diseases such as Systemic Lupus Erythematosus (SLE), Mixed Connective Tissue Disease (MCTD), Undifferentiated Connective Tissue Disease (UCTD), Sjögren's Syndrome (SS), Scleroderma (Systemic Sclerosis), Dermatomyositis, Polymyositis, Rheumatoid Arthritis (RA), CREST Syndrome, and Raynaud's Phenomenon.

Historically, the most common test for antinuclear antibodies has been Immunofluorescence Assay (IFA).  It uses controlled cell lines (frequently HEp-2000) that are fixed on a slide. The cells can contain as many as 120 different antigens used for the diagnosis of autoimmune disorders. When diluted human sera containing autoantibodies are spread over the mounted cells, the antibodies bind to the cellular antigens. Typically, they are then detected by the application of anti-human immunoglobulins, labeled with a fluorescent dye. Sometimes, non-clinically relevant autoantibodies are detected in patient samples and can be interpreted as clinically “false positive”.  The HEP-2000 ANA test is the first part of our testing algorithm.     Also included in this first part are antibodies to Cyclic Citrullinated Peptide (CCPT), which is helpful in the diagnosis of rheumatoid arthritis.

Enzyme Immunoassay (EIA) technology can also be employed for autoimmune testing.  This is the reflex part of our testing algorithm. EIA relies upon mixtures of common antigens to detect antibodies associated with autoimmune diseases. These common antigens vary among EIA manufacturers. In EIA testing, diluted sera are mixed with the antigens bound to a solid phase (most commonly a microtiter plate). Autoantibodies that bind to the plate are then detected with anti-human IgG coupled to an enzyme that can be utilized to produce a colorimetric signal. EIA technology, when applied to ANA testing, produces a “composite” signal. However, a strong signal from one antibody is not distinguishable from a number of weak signals to multiple antibodies. There is still a risk of false positives in EIA tests due to non-specific binding of other IgG antibodies to the solid phase.