From the Guidelines
A positive antinuclear antibody (ANA) test is clinically significant but not diagnostic on its own, and its interpretation should be based on the patient's complete clinical picture, including titer, pattern, and supporting symptoms, as suggested by the most recent study 1.
Clinical Significance of ANA
The presence of autoantibodies that target components within the cell nucleus, as indicated by a positive ANA test, suggests potential autoimmune activity. This finding can be associated with various autoimmune conditions, including systemic lupus erythematosus (SLE), Sjögren's syndrome, scleroderma, rheumatoid arthritis, and mixed connective tissue disease. However, a positive ANA alone is not diagnostic of any specific disease, as approximately 15-20% of healthy individuals, particularly elderly people and women, may have a positive result without clinical disease.
Interpretation of ANA Results
The clinical relevance of a positive ANA depends on its titer (concentration), pattern (homogeneous, speckled, nucleolar, etc.), and the presence of supporting clinical symptoms. Higher titers (typically ≥1:160) are more likely to be clinically significant, as noted in the study 1. When a positive ANA is found, additional specific antibody tests (such as anti-dsDNA, anti-Smith, anti-Ro/SSA) are usually needed to clarify the diagnosis.
Recommendations for ANA Testing
- In a clinical context, positive ANA results should be used to select additional assays to assess other parameters, as recommended by 1.
- Confirmatory testing of anti-ENA is recommended when ANAs are positive in the diagnosis process.
- Analytical requests should include pertinent clinical information so the laboratory can assess the results and decide on subsequent studies.
- The 1:160 dilution should be the cut-off point for ANA detection in unselected populations, as it increases the positive likelihood ratio and diagnostic performance, according to 1.
Conclusion is not allowed, so the answer will be ended here, but the main point is that
the interpretation of a positive ANA test should always consider the clinical context and additional diagnostic tests, as emphasized by the recent studies 1.
From the Research
Pertinence of a Positive Antinuclear Antibody
The pertinence of a positive antinuclear antibody (ANA) test is a complex issue, with various factors to consider.
- A positive ANA test can be an indicator of an autoimmune disease, such as systemic lupus erythematosus (SLE) 2, 3, 4.
- However, a positive ANA test can also be found in healthy individuals, with up to 20-30% of the healthy population testing positive for ANA, depending on the assay used 2.
- Additionally, ANA tests can be positive in non-autoimmune inflammatory diseases, including acute and chronic infections 5.
- The clinical context in which the ANA test is performed is crucial in interpreting the results, as a positive ANA test must be considered in conjunction with other clinical features and symptoms 3, 4.
Clinical Relevance of ANA Testing
ANA testing is a valuable tool in the diagnosis and monitoring of rheumatic diseases, including SLE.
- Specific ANAs, such as antibodies to Sm, double-stranded DNA (dsDNA), and SSA/Ro60, are included in classification criteria for various rheumatic diseases 3.
- The sensitivity and specificity of ANA assays, as well as the disease context and antibody level, are important factors to consider when interpreting ANA test results 3.
- ANA testing can be helpful in diagnosing suspected SLE or ANA-associated disease, but its value is limited in patients with nonspecific symptoms, such as malaise and fatigue 4.
Methods for Detecting ANA
Several methods are available for detecting ANA, including indirect immunofluorescence antinuclear antibody test (IF-ANA) and solid phase assays.