Antinuclear Antibodies (ANA) are proteins generated by the immune system that can mistakenly target the body’s own healthy tissues. An ANA test is a common screening tool used to investigate potential immune system irregularities, helping determine if these autoantibodies are present.
Understanding ANA Testing
The immune system produces antibodies to neutralize foreign invaders. Autoantibodies, however, incorrectly target the body’s own cells and tissues, leading to autoimmune conditions.
The ANA test is a blood test involving a sample drawn from a vein in the arm. This sample is analyzed in a laboratory, often using indirect immunofluorescence (IIF), where antinuclear antibodies are made to glow under a microscope.
The primary reason for ordering an ANA test is to screen for systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), Sjögren’s syndrome, scleroderma, and mixed connective tissue disease. While a positive ANA result indicates autoantibodies, it is a screening tool, not a definitive diagnosis. It helps healthcare providers assess the likelihood of an autoimmune disease when combined with symptoms and other tests.
Interpreting Your ANA Results
ANA test results are typically reported as negative or positive. A negative result suggests antinuclear antibodies were not detected, making an autoimmune disorder less likely. A positive result means these autoantibodies were found, but it does not automatically confirm an autoimmune disease, as many healthy individuals can have a positive result.
When a test is positive, the result includes a “titer,” which indicates the concentration of autoantibodies in the blood. A titer is expressed as a dilution ratio, such as 1:40, 1:80, or 1:160. A higher titer, for example, 1:320 compared to 1:40, signifies a greater concentration of ANAs. While higher titers generally suggest a higher likelihood of an autoimmune disease, even low titers can be seen in healthy people.
The test also identifies specific “patterns” of fluorescence observed under the microscope, which can offer clues about the type of autoimmune disease that might be present.
Homogeneous pattern: Entire nucleus stains uniformly, often associated with systemic lupus erythematosus or drug-induced lupus.
Speckled pattern: Appears as fine or coarse dots, suggesting connective tissue diseases like Sjögren’s syndrome or mixed connective tissue disease.
Nucleolar pattern: Staining around the nucleoli, frequently seen in scleroderma.
Centromere pattern: Distinct dots at the chromosomes, strongly linked to limited forms of scleroderma.
Why ANA Results Can Vary
ANA test results can fluctuate due to various biological and external factors. Minor variations in immune system activity are normal and can lead to transient changes in ANA levels.
Certain medications can induce a temporary positive ANA result, including blood pressure medications (e.g., hydralazine), anti-arrhythmics (e.g., procainamide), antibiotics (e.g., minocycline), TNF-alpha inhibitors, and certain anticonvulsants. Drug-induced positive ANAs often resolve once the medication is discontinued.
Infections can also trigger a temporary positive ANA. Acute viral infections (e.g., Epstein-Barr virus, hepatitis B or C, HIV, parvovirus B19, COVID-19) and bacterial infections (e.g., Lyme disease, syphilis, tuberculosis) may cause ANA production. These antibodies often disappear once the infection clears.
Non-autoimmune conditions can occasionally result in a positive ANA, including certain cancers, chronic liver diseases, and thyroid disorders. Fibromyalgia has also been associated with positive ANA results in some individuals. In these situations, ANA positivity does not indicate an underlying autoimmune disease.
Age and gender influence ANA prevalence. The likelihood of having a positive ANA increases with age, and women are more likely to have positive ANA results than men. Pregnancy can also lead to a transient positive ANA result, which does not necessarily indicate an underlying autoimmune disease. Laboratory factors, such as differences in testing methodologies (e.g., indirect immunofluorescence assay (IFA) versus ELISA), variations in specific laboratory kits, or even subjective interpretation between different laboratories, can contribute to variations in reported ANA results. For individuals already diagnosed with an autoimmune condition, changes in ANA titer or pattern might reflect fluctuations in disease activity, such as flares or periods of remission.
Navigating Changes in ANA Results
If your ANA results have changed or are unexpected, consult with a healthcare professional. A positive ANA test is one piece of information and must be interpreted within the context of your overall clinical picture, including your symptoms and medical history.
Your doctor will likely evaluate your clinical symptoms thoroughly and review your medical history to understand the significance of the changing ANA results. This evaluation may involve a physical examination to check for signs associated with autoimmune conditions. To further investigate, your doctor might order repeat ANA tests or more specific antibody tests, such as an ENA (Extractable Nuclear Antigen) panel, anti-dsDNA, anti-Sm, anti-Ro/SSA, or anti-La/SSB antibodies. These additional tests help to identify more specific autoantibodies that are more strongly linked to particular autoimmune diseases. The information from these tests, combined with other diagnostic criteria, will help your healthcare provider determine the appropriate next steps.