What is an Antinuclear Antibody Test?

An antinuclear antibody test is a type of laboratory test which looks for antinuclear antibodies, a special type of antibody linked with certain medical conditions. This type of test is most commonly ordered when a patient is believed to have systemic lupus erythematosus (SLE), although it can be ordered in other situations as well. A positive or negative result on this test cannot be used alone for a diagnosis, but it can be used in the evaluation of a patient who has come to the doctor complaining of health problems.

Antinuclear antibodies are antibodies which are designed to bind to the nuclei of cells in the body. This is rather unusual, as antibodies are usually designed to repel foreign invaders. People with autoimmune disorders often test positive for high numbers of antinuclear antibodies, although these antibodies can also be linked with other ongoing disease processes such as infections, hormone imbalances, blood diseases, skin conditions, and gastrointestinal problems, among others. Some patients also have naturally high levels with no apparent cause.

In an antinuclear body test, a sample is drawn from the patient and a serum is prepared. The serum is used to wash a plate of commercially prepared cells. If the serum contains antinuclear antibodies, it will bind to the cells on the plate. When the preparation is treated with an antibody which tags the antinuclear antibodies and fluoresces, the levels of antinuclear antibodies will be clearly visible.

The results for the antinuclear antibody test usually present a result in terms of a titer, rather than just stating that the test is positive or negative. A low titer is less of a cause for concern than a high one. People normally have small amounts of antinuclear antibodies in their bodies, and these levels can fluctuate in response to ongoing medical issues, making the expression of a titer especially important because it demonstrates not only that antinuclear antibodies are present, but how prevalent they are.

Test results may also refer to patterns. Certain patterns of antinuclear antibodies are associated with particular autoimmune conditions. Some examples of patterns which may emerge during an antinuclear antibody test include speckled, homogenous, and nucleolar patterns. These can be used as an indicator to learn more about a patient's condition.

If an antinuclear antibody test is positive with a high titer, additional follow-up will be needed before a doctor can provide a firm diagnosis. This can include testing, observation of the patient, and other diagnostic techniques. In addition to being used to explore the possibility of an autoimmune condition, an antinuclear antibody test may also be used in a workup of a patient complaining of infertility, because high levels of antinuclear antibodies are linked with fertility problems.