What is ANA - IFA?
ANA refers to Antinuclear antibodies. These are antibodies produced by the immune system of the body against protein markers found in the nucleus of its own cells. The Antinuclear Antibody Test measures the amount and pattern of antinuclear antibodies in the blood.
Why is ANA - IFA done?
- To determine the presence of an autoimmune disease like Systemic Lupus Erythematosus (SLE)
- To evaluate the possible presence of autoimmune Connective Tissue Disorders (CTDs) other than SLE such as Polymyositis, Scleroderma, Sjögren's syndrome etc.
What does ANA - IFA Measure?
The Antinuclear Antibody (ANA) test measures the amount and pattern of antinuclear antibodies in the blood. The immune system of the body is responsible for differentiating between the body’s own cells and foreign cells, like pathogens. Once the foreign cells are identified, they are then targeted and destroyed. In autoimmune disorders, the immune system of the body is unable to recognize certain cells as the body’s own cells and starts an immune response against them which results in their destruction. The recognition of ‘self’ and ‘non-self’ cells is mediated by certain proteins present on the surface of cells or inside them. When the immune system identifies a cell as foreign or ‘non-self’, it produces antibodies against these cells to destroy them. Antibodies produced in an autoimmune disease are called autoantibodies.
Antinuclear antibodies (ANA) are autoantibodies that are produced against protein markers present in the nucleus of certain cells of the body. They are produced in a number of autoimmune diseases but are most commonly produced in Systemic Lupus Erythematosus (SLE).
The Antinuclear Antibody Test can be performed either by Immunoassay method or Indirect Fluorescent Antibody (IFA) method to detect ANA in blood. Both these tests may be used by some laboratories together: the Immunoassay method screens for the presence of antinuclear antibodies, and the IFA method subsequently confirms the positive or equivocal Immunoassay results.
Interpreting ANA - IFA results
The appearance of fluorescence is a positive result and indicates the presence of antinuclear antibodies.
The absence of fluorescence is a negative result and indicates the absence of antinuclear antibodies.
Positive results of IFA are expressed in two parts: as titers which are ratios that represent the highest dilution of the blood sample at which antinuclear antibodies were visible, and as the fluorescent pattern is seen. Titer value indicates the number of antinuclear antibodies in the blood, while the pattern of fluorescence indicates different autoimmune diseases.