What is an ANA Test?

An ANA test, also known as the antinuclear antibody test, is designed to detect antinuclear antibodies in a sample of blood. The acronym ANA refers to antinuclear antibodies that are automatic in the sense that they automatically bind to certain surfaces within the nucleus of cells. While a healthy person should possess a certain amount of antibodies to guard against invading bacteria, antinuclear antibodies work against this self-defense mechanism. In fact, a high level of antinuclear antibodies present may indicate that the immune system is capable of mistakenly launching an attack on healthy tissue. This condition is known as autoimmunity.

The ANA test was developed by Dr. George Friou in 1957 to help diagnose autoimmune disorders. Most commonly, an ANA test is performed when lupus is suspected. However, the clinician may order an ANA test to rule out various other autoimmune disorders when certain symptoms are present, such as frequent joint pain, skin rashes, chronic fatigue, or a persistent low-grade fever. Additional blood tests may be performed in addition to the ANA test, to include erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) tests. Often, the results of each blood test can be determined from a single serum sample.

ANA tests allow the clinician to examine how certain antibodies react to the nucleus of cells In vitro. When a reaction is observed, they are then said to be antinuclear antibodies. Sometimes, it is necessary to use fluorescence tools to determine if there is an antinuclear reaction. For this reason, the ANA test is sometimes referred to as the fluorescent antinuclear antibody test, or FANA.

Antinuclear antibodies, or ANAs, can also be present in patients without autoimmune disorders. For instance, ANAs may be detected in those afflicated with kidney, liver, breast, or other types of cancer. ANAs may also be found in persons with chronic infectious diseases. In addition, a positive ANA test result may occur in subjects with Crohn's disease, Grave's disease, ulcerative colitis, Addison disease, rheumatoid arthritis, and many other disorders. In addition, about five percent of the population exhibits low levels of ANAs without any disease being present.

A positive ANA test result may also be drug-induced. For instance, procainamide, dilantin, and hydralazine are medications known to promote the production of ANAs. In this case, the elevated levels of ANA may not be related to any disease. However, if a disease is diagnosed, it is said to be a drug-induced disease.

Aside from determining the number of ANAs present during an ANA test, the clinician also observes ANA patterns. Specifically, this observation is dependent on the type of stain used on the nucleus of the cell, which results in homogeneous or diffuse, peripheral or rim, speckled, or a nucleolar pattern. No one pattern is specific to any particular disease. However, certain diseases are more commonly linked to certain patterns. For instance, the nucleolar pattern is most commonly found in people with scleroderma.