From the Guidelines
An ANA titer of 1:80 with a nuclear, homogeneous pattern and Actin less than 20 is considered positive, but its specificity for Systemic Lupus Erythematosus (SLE) is relatively low at 74.7%.
Interpretation of Results
- The result should be interpreted with caution, considering the clinical context and other laboratory findings, as the positive likelihood ratio is low 1.
- A nuclear, homogeneous pattern is commonly seen in SLE, but it can also be found in other autoimmune disorders and healthy individuals 1.
- The presence of Actin less than 20 does not provide additional diagnostic information in this context.
Clinical Implications
- The EULAR/ACR 2019 classification criteria consider ANA titers ≥1:80 as a required entry criterion for SLE classification, but this criterion has limited use in diagnosing or screening for SLE 1.
- In clinical practice, ANA tests should be requested with pertinent clinical information to guide further testing and interpretation of results 1.
- Additional assays, such as anti-ENA or anti-dsDNA, may be necessary to increase the diagnostic specificity and positive predictive value 1.
Laboratory Considerations
- The laboratory report should detail the method used for ANA detection, and results should be interpreted in the context of the clinical presentation and other laboratory findings 1.
- The use of international units (IU) and likelihood ratios can help standardize the interpretation of laboratory results, but the lack of standardization in autoantibody assays remains a challenge 1.
From the Research
Interpretation of ANA Titer and Pattern
The interpretation of an Antinuclear Antibody (ANA) titer of 1:80 with a nuclear, homogeneous pattern and Actin less than 20 can be understood through the following points:
- ANA testing is used to diagnose systemic autoimmune rheumatic disease (SARD) 2, 3, 4, 5, 6.
- A homogeneous pattern on ANA-HEp-2 cells can result from various antibodies, including anti-double-stranded DNA (dsDNA), anti-nucleosome, anti-histone, anti-Scl-70, or anti-dense fine speckles 70 (DFS70) antibodies 3.
- The study by 4 found that ANA titration of equal or more than 1:320 can be used as the best titration for differentiating between SARDs and non-SARDs in a positive ANA sample, but the homogeneous pattern was also significantly associated with SARDs.
- The pattern on the ANA-HEp-2 test is a critical parameter for discriminating ANA-positive healthy individuals and patients with autoimmune rheumatic diseases 6.
- Nuclear homogeneous patterns appeared exclusively in patients with ARDs in the study by 6, suggesting that this pattern may be more indicative of autoimmune disease.
Key Findings
- ANA titer and pattern are important for diagnosing SARDs 4, 6.
- Homogeneous pattern is associated with SARDs, particularly systemic lupus erythematosus (SLE) 4, 6.
- Actin less than 20 is not directly addressed in the provided studies, but the focus is on the interpretation of ANA titer and pattern.
Study Implications
- The studies suggest that a positive ANA result, particularly with a homogeneous pattern, should be interpreted in the context of clinical symptoms and other diagnostic criteria for SARDs 2, 3, 4, 5, 6.
- Further testing and evaluation may be necessary to confirm a diagnosis of SARD or to rule out other conditions 2, 3, 4, 5, 6.