Antinuclear Antibody Test for Diagnosing Autoimmune Diseases
One of the first medical tests done to diagnose autoimmune diseases is Antinuclear Antibody test. The primary objective of antinuclear antibody tests is to diagnose the presence of antibodies that attack the body’s own cells. Let us first understand the difference between different types of antibodies.
Antibodies are immunoglobulin protein structures produced by ?-lymphocytes cells of immune system in response to substances or microorganisms which are foreign to the body’s system.
Autoantibodies are the antibodies that are produced by the immune system when its ability to differentiate between the foreign substances and body’s own cells is masked. The autoantibodies act against body’s own cells and tissues causing their death.
Antinuclear Autoantibodies are the ones that attack the nuclear substance or the matter present in the nucleus of the cells.
When is Antinuclear Antibody Test Done ?
- An antinuclear antibody test is done when a person is suspected to have developed symptoms of an autoimmune disease.
- When a person already suffering from a certain type of autoimmune disorder starts aggravated signs and their doctor suspects them to have developed additional autoimmune disease then the antinuclear antibody test is ordered.
Disease diagnosed by Antinuclear Antibody Test
- Rheumatoid Arthritis : it is a disease that weakens the connective tissue in muscles, bones and joints.
- Sjogren’s syndrome
- Systemic Lupus Erythemetosus (SLE)
Fluorescent Antinuclear Antibody Test
The most common test assay is immunofluorescence microscopy. The serum sample of the patient is added to the cell culture. The antinuclear antibodies, if present, would bind to the cell nuclei and form a complex. Next, a fluorescent tagged antibody is added to the culture. This secondary antibody binds to the antinuclear antibody and cell nuclei complex and glows due to fluorescence under a microscope.
The results of the antinuclear antibody tests are reported as titer with immunofluorescence pattern. The last dilution titer with fluorescence is always reported as the antinuclear antibody tests results and the specific patterns in fluorescence signify different autoimmune diseases. Low levels of titer are considered as negative however, high levels of titer such as 1:350 are considered positive results.
Mostly people with SLE and rheumatoid arthritis will result positive for antinuclear antibody tests. Though there can be false positives also as in some healthy people may also test positive. Once a person tests positive, more tests follow antinuclear antibody test to confirm the presence specific autoantibodies.