What pattern commonly shows up in false positive Antinuclear Antibody (ANA) testing?

From the Guidelines

The most common pattern that shows up in false positive antinuclear antibody (ANA) testing is the speckled pattern, particularly the dense fine speckled (DFS) pattern, as noted in the context of ANA testing standardization efforts 1.

When considering the patterns that commonly show up in false positive ANA testing, several factors come into play, including the method of testing, the titer at which the test is considered positive, and the clinical context of the patient. The speckled pattern, especially the dense fine speckled pattern, is highlighted due to its frequent appearance in false positives. This is crucial because false positive ANA results can occur in a significant percentage of healthy individuals, particularly at lower titers such as 1:40 or 1:80.

Key points to consider in the context of false positive ANA testing include:

• The role of indirect immunofluorescence assay (IIFA) as a reference method for ANA testing, as emphasized by international recommendations 1.
• The importance of defining nuclear and cytoplasmic staining patterns to accurately interpret ANA test results.
• The potential for false positives due to various factors such as medications (e.g., procainamide, hydralazine, and isoniazid), acute or chronic infections, inflammatory conditions, advanced age, and family history of autoimmune disease.
• The need for additional specific antibody tests, like anti-dsDNA or anti-ENA panel, when an ANA test shows a positive result but doesn't correlate with clinical symptoms of autoimmune disease.

The mechanism behind these false positives often involves non-pathogenic antibodies that react with nuclear antigens without causing disease or cross-reactivity with similar epitopes found in medications or infectious agents. Given the complexities and potential for false positives, it is essential to interpret ANA test results in the context of clinical symptoms and consider additional testing to determine clinical significance, as suggested by the international recommendations for ANA testing 1.

From the Research

Patterns in False Positive ANA Testing

• A positive ANA test can appear as different morphological patterns, some of which are associated with specific autoantibodies relevant to certain diseases, while others occur mainly in non-related conditions or even in healthy individuals 2
• The HEp-2 IFA test can detect a wide spectrum of autoantibodies, but only some patterns are associated with specific autoantibodies relevant to diseases such as SLE, JIA, AIH, and PBC 2
• Certain patterns, such as the homogeneous or speckled pattern, are more commonly associated with false positive results, while others, such as the nucleolar or centromere pattern, are more specific for certain diseases 3, 2
• The presence of ANA can be associated with numerous non-rheumatic factors, including environmental exposures, malignancies, drugs, and infections, which can lead to false positive results 4
• In the absence of connective tissue disease symptoms, a positive ANA test has minimal clinical significance in diagnosing rheumatic diseases, and further investigation may not be warranted 4

Clinical Implications

• Screening for autoantibodies against other anti-ENAs seems mandatory in RA patients, especially when ANA is positive, to rule out other autoimmune diseases 5
• The simultaneous presence of lymphoproliferative diseases and rheumatic syndromes is more frequent among lymphoma patients than in other lymphoproliferative diseases, and screening for antibodies in these patients may be useful for discovering underlying autoimmune diseases 6
• Understanding the clinical relevance of different ANA patterns and the disease context is crucial for accurate interpretation of ANA test results and to avoid unnecessary referrals and costly workups 3, 4