From the Guidelines
The Antinuclear Antibody (ANA) pattern is typically determined by indirect immunofluorescence assay (IIFA) and can be reported according to standardized terminology, including nuclear, cytoplasmic, and mitotic apparatus patterns.
Key Points
- The IIFA is considered the reference method for ANA screening, and alternative assays can be used while keeping in mind that false negative and false positive ratios of these methods may be different 1.
- ANA-IIFA patterns should be reported according to standardized terminology, and besides nuclear patterns, cytoplasmic and mitotic apparatus patterns should be reported and specified when possible 1.
- The detection of ANA is the first level test for laboratory diagnosis of systemic autoimmune rheumatic diseases (SARD), and ANA testing is primarily intended for diagnostic purposes, and not for monitoring disease progression 1.
- A proper ANA-IIFA is dependent on reagents, equipment, and other local factors, thus the screening dilution should be defined locally, and an abnormal ANA should be the titre above the 95th percentile of a healthy control population 1.
- In the case of a positive ANA test, it is recommended that the pattern and the highest dilution to demonstrate reactivity be reported 1.
Evidence
The international recommendations for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies suggest that ANA detection by IIFA is the first level test for laboratory diagnosis of SARD, and that ANA testing is primarily intended for diagnostic purposes 1. The recommendations also emphasize the importance of defining nuclear and cytoplasmic staining, and the need to incorporate alternative automated methods 1. Additionally, the recommendations suggest that ANA-IIFA patterns should be reported according to standardized terminology, and that besides nuclear patterns, cytoplasmic and mitotic apparatus patterns should be reported and specified when possible 1. It is also recommended that the pattern and the highest dilution to demonstrate reactivity be reported in the case of a positive ANA test 1. The use of a screening dilution of 1:160 on conventional HEp-2(000) substrates is often suitable for the detection of ANA in adult populations being evaluated for SARD 1. However, it is essential to note that the specificity of ANA detection for SLE is relatively low, with a specificity of 74.7% (IC 95%: 66.7% - 81.3%) when using a cut-off point of 1:80 1. Therefore, caution is necessary when using ANA detection as a diagnostic criterion for SLE, and it is essential to consider the clinical context and other diagnostic criteria 1.
From the Research
Antinuclear Antibody (ANA) Patterns
The Antinuclear Antibody (ANA) test is used to diagnose and classify systemic lupus erythematosus (SLE) and other autoimmune diseases. The ANA pattern can provide useful information in SLE diagnosis.
- The most common ANA patterns are:
- Homogeneous pattern: associated with oral/nasal ulcers and non-scarring alopecia 2
- Speckled pattern: associated with fever, acute and chronic cutaneous lupus, arthritis, serositis, hematologic involvement, renal involvement, neuropsychiatric involvement, gastrointestinal involvement, and cardiopulmonary involvement 2
- Dense fine speckled pattern: associated with systemic lupus erythematosus (SLE) and autoantibodies against nucleosome and ribosomal P0 3
- Reticular pattern: associated with primary biliary cholangitis and autoantibodies against M2 3
- Other uncommon patterns of ANA include:
- The frequency of ANA patterns can vary depending on the population and the assay used. For example, one study found that 82.4% of SLE patients had a positive ANA test, with 46.1% having a speckled pattern and 42.4% having a homogeneous pattern 5.
- The clinical significance of ANA patterns is not fully understood and requires further study. However, it is clear that ANA testing is an important tool in the diagnosis and classification of autoimmune diseases, including SLE 6.