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◉ What is ANA test?
The ANA test is a laboratory test used to detect the presence of antinuclear antibodies in the blood. A positive result means that you have a higher amount of antinuclear antibodies than normal, and that should be further examined.
Antibodies are proteins produced by your immune system to combat invading foreign substances like viruses and bacteria. In certain cases, such as with antinuclear antibodies (ANA), these proteins mistakenly target the body's own cells as foreign, leading to various forms of damage.
ANA test is an important tool in diagnosing and monitoring various autoimmune disorders, such as lupus, rheumatoid arthritis, scleroderma, Sjogren's syndrome and more.
It's important to note that this test is a screening test and does not provide a precise diagnosis. If you receive a positive result, your doctor will recommend more specific tests for further evaluation.
◉ ANAs subtypes
Antinuclear antibodies comprise a diverse group of autoantibodies directed against multiple antigens at various cellular compartments (chromatin, nucleoli, nucleoplasm, cytosol, mitotic spindle apparatus ).
Currently, ANAs have been classified into 2 main groups:
Autoantibodies to DNA and histones
- Anti-dsDNA Antibodies: Highly specific for SLE and are found in a significant number of SLE patients.
- Anti-Histone Antibodies: Commonly seen in drug-induced lupus.
Autoantibodies to extractable nuclear antigens (ENA)
- Anti-Ro (SSA) and Anti-La (SSB) Antibodies: Associated with conditions like Sjögren's syndrome and systemic lupus erythematosus (SLE).
- Anti-Sm Antibodies: Often found in SLE and are quite specific to this disease.
- Anti-nRNP Antibodies: Associated with mixed connective tissue disease.
- Anti-Scl-70 (Topoisomerase I) Antibodies: Typically seen in systemic sclerosis (scleroderma), particularly the diffuse form.
- Antibodies to Nuclear Pore Complexes: Associated with specific autoimmune conditions and sometimes cancers.
- Anti-Centromere Antibodies: Linked to limited systemic sclerosis (limited scleroderma) and conditions like Raynaud's phenomenon.
- Anti-Sp100 Antibodies: Associated with primary biliary cholangitis (also known as primary biliary cirrhosis).
◉ Why the test is Performed
The purpose of an ANA test is to help healthcare professionals in several ways:
- Diagnosing Autoimmune Disorders: This test allows the doctor to quickly assess whether symptoms you have, such as extreme fatigue, joint pain, or skin rashes, are associated with an autoimmune condition.
- Monitoring Disease Activity: In individuals already diagnosed with autoimmune disorders, the antinuclear antibodies test can be used to monitor disease activity and response to treatment.
- Identifying Specific Patterns: The ANA test can reveal specific patterns (e.g., speckled, homogeneous, nucleolar) of antibody binding to the nucleus. These patterns may help guide the diagnosis and classification of certain autoimmune diseases.
◉ How can I prepare for the test?
To prepare for the ANA blood test, you do not need to do anything special. However, you should tell your doctor about any medications or supplements that you are taking, even over-the-counter ones. Some drugs, such as certain seizure and heart medications, can affect the accuracy of the test.
The antinuclear antibody test is a simple blood test that does not require fasting or any other dietary restrictions.
◉ Normal range
The antinuclear antibody test does not have a single universally defined normal range.
The ANA test results are typically reported as a titer and pattern. The titer indicates the level or concentration of antibodies, while the pattern describes the specific appearance of the antibody binding to the nucleus of cells.
The reference technique for the detection of antinuclear antibodies is the indirect immunofluorescence (IFI) technique on HEp2 cells (Human Epithelial Cell Line Type 2).
1. The titer of ANA test
- A low level of ANA (such as 1:40 or 1:80) is considered normal or negative.
- A high level of ANA (such as 1:160 or higher) is considered abnormal or positive.
2. The pattern of ANA test
- Homogenous pattern (H-ANA).
- Speckled pattern (S-ANA).
- Nucleolar pattern (N-ANA).
- Cytoplasmic pattern (C-ANA).
- Centromere pattern (Cen-ANA).
- Mitochondrial pattern (M-ANA)
- Mixed patterns such as Speckled + Cytoplasmic (SC-ANA), Homogenous + Mitochondrial (HM-ANA), Homogenous + Nucleolar (HN-ANA).
◉ A positive result on an ANA test
It's normal to have some ANAs, but having too many of these proteins is a sign of an active autoimmune disease.
1. Can high ANA results be seen in healthy people?
Positive titers of ANA can be observed in people without any detectable disease, especially with low titers. However, high results are usually associated with clinical manifestations.
2. Causes
Causes of positive results of ANA may be various, encompassing both autoimmune and non-autoimmune diseases. Here are some examples:
- Systemic Lupus Erythematosus.
- Rheumatoid arthritis.
- Systemic sclerosis (scleroderma).
- Sjögren's syndrome.
- Mixed connective tissue disease (MCTD).
- Dermatomyositis and Polymyositis.
- Systemic sclerosis.
- Autoimmune hepatitis.
- Autoimmune thyroiditis
- Infections: Hepatitis, HIV, Epstein-Barr virus, and tuberculosis.
- Cancers: Leukemia and lymphoma.
- Medications: Some drugs can induce ANA production in some people, such as certain seizure and heart medications, antibiotics, and anti-inflammatory drugs.
- Aging: As people get older, their immune system may become less efficient and more prone to produce ANA. This does not necessarily mean that they have an autoimmune disease, but it may increase their risk of developing one.
2. Symptoms of Positive ANA
Symptoms associated with high ANA test levels may include:
- Fatigue and malaise
- Joint pain and swelling
- Muscle pain and weakness
- Skin rashes or lesions
- Photosensitivity (increased sensitivity to sunlight)
- Raynaud's phenomenon (color changes in fingers and toes in response to cold or stress)
- Dry eyes and mouth (in Sjögren's syndrome)
- Organ-specific symptoms (e.g., kidney involvement in lupus)
◉ Low values of ANA test
- Absence of Autoimmune Disorders: A negative ANA test indicates the absence of detectable antinuclear antibodies in the blood. In such cases, the cause of symptoms may be attributed to other conditions or factors that are not autoimmune-related.
- Early Disease Stage: In some cases, individuals with autoimmune disorders may have negative ANA test results early in the disease course. As the disease progresses, the ANA test may become positive.
◉ Additional tests
- Erythrocyte Sedimentation Rate (ESR): It measures the rate at which red blood cells settle in a test tube over a specified period, which can be associated with RA and other inflammatory conditions.
- C-Reactive Protein (CRP): It measures the level of C-reactive protein in the blood, a protein produced by the liver in response to inflammation that can be elevated in RA and other inflammatory conditions.
- Anti-double-stranded DNA (anti-dsDNA) test: This test detects antibodies that target the double-stranded DNA, which is the genetic material of the cell.
- Anti-histone test: This test detects antibodies that target the histone, which is a protein that helps in DNA packaging and regulation.
- Anti-RNP Antibody: This test detects antibodies targeting ribonucleoproteins (RNPs), which shares features of multiple autoimmune disorders.
- Anti-centromere test: This test detects antibodies that target the centromere, which is a part of the cell that helps in cell division.
◉ Conclusion
In conclusion, the antinuclear antibody (ANA) test is a crucial diagnostic tool in the field of rheumatology and autoimmune diseases.
This test detects the presence of antibodies that target components of the cell nucleus, so it provides important information for healthcare professionals in identifying potential autoimmune disorders and guiding further diagnostic investigations
