Antinuclear Antibody: Reference Range, Interpretation, Collection and Panels (original) (raw)

ANA tests identify antibodies present in serum that bind to autoantigens present in the nuclei of mammalian cells. Most of these antibodies are IgG, but IgM and IgA have also been detected. The ELISA method involves the interaction of these antibodies present in the serum sample with a preprepared antigen and the addition of an antibody that adheres to this complex and induces a color change; the result is an optical density value (a photometric scale) that is read as positive, negative, or equivocal.

The IFA method used in most laboratories uses human tumor cell-line substrate (the HEp-2 cell line) to detect the presence of these antibodies in human serum. A fluorescent-labeled antibody adheres to this antigen-antibody complex and allows visualization of the pattern. Any pattern visualized at a 1:40 dilution should be titered to end dilution (ie, the first dilution at which pattern can no longer be visualized). [3, 4, 5]

ANA is the screening method of choice for systemic rheumatic diseases (sometimes referred to as connective tissue or collagen diseases) such as systemic lupus erthyematosus (SLE), mixed connective tissue disease, Sjögren syndrome, scleroderma, CREST syndrome, rheumatoid arthritis, polymyositis, and dermatomyositis. [6]

Research has indicated that a link exists between ANAs and coronavirus disease 2019 (COVID-19). A study by De Santis et al, for example, found that out of 35 patients with COVID-19, 20 (57%) had ANAs. [7]

Drugs (ie, procainamide, phenytoin, penicillin, and hydralazine), neoplasms, chronic liver disease, viral illnesses, and chronic infections may result in low titers of ANAs. Elderly and otherwise healthy persons may also have low titers.

Patients with SLE receiving steroids may have negative test results. Some patients with SLE may have a negative ANA test.

In addition, in patients with SLE, the ANA level can change over time not only as a result of immunosuppressive agents, but also owing to the disease’s natural history. Important information regarding the disease’s mechanisms and status could be derived through rescreening for ANA concentrations following SLE’s onset. [8]

No conditions exist under which this test should not be performed.