How to proceed with a patient who has a positive anti-DNA (anti-deoxyribonucleic acid) antibody test but an otherwise normal Antinuclear Antibody (ANA) comprehensive panel?

Management of Positive Anti-DNA Antibody with Otherwise Normal ANA Panel

Confirm the anti-DNA result with a second method (CLIFT if the initial test was a solid-phase assay, or vice versa) and assess for clinical signs of systemic lupus erythematosus (SLE), as isolated anti-dsDNA positivity without ANA positivity is uncommon and may represent a false positive or early/evolving disease. 1

Understanding the Discordant Result

This scenario—positive anti-dsDNA with negative ANA—is unusual because:

• Anti-dsDNA antibodies are typically detected in the context of a positive ANA, as ANA is the first-level screening test for systemic autoimmune rheumatic diseases (SARD) and should be positive before pursuing anti-dsDNA testing 1
• The standard diagnostic algorithm recommends anti-dsDNA testing only when ANA is positive and there is clinical suspicion of SLE 1
• However, testing for specific antibodies should be granted in cases of high clinical suspicion regardless of ANA result, as some autoantibodies may be present in ANA-negative patients 1, 2

Immediate Confirmatory Testing

Verify the Anti-DNA Result

• Use a double-screening strategy with two different methodologies: if the initial positive result was from a solid-phase assay (ELISA, FEIA, CLIA), confirm with Crithidia luciliae immunofluorescence test (CLIFT), which offers high clinical specificity but lower sensitivity 1
• If the initial test was CLIFT (highly specific), repeat with a solid-phase assay to assess concordance 1
• Report results quantitatively or semi-quantitatively to establish a baseline for potential future monitoring 1

Verify the ANA Result

• Confirm that ANA was performed by indirect immunofluorescence assay (IIFA) on HEp-2 cells, as this is the reference method and alternative automated methods may yield false negatives 1
• If ANA was performed by a non-IIFA method and is negative, repeat using IIFA when clinical suspicion is strong 1
• Ensure the screening dilution was appropriate (typically 1:160 for adults), as lower dilutions may miss clinically significant antibodies 1

Clinical Assessment for SLE

Evaluate for specific clinical manifestations of SLE:

• Malar or discoid rash, photosensitivity, oral ulcers 2
• Inflammatory arthritis (non-erosive, involving two or more peripheral joints) 2
• Serositis (pleuritis or pericarditis) 2
• Renal involvement: obtain urinalysis for proteinuria and hematuria to screen for lupus nephritis 2
• Hematologic abnormalities: obtain complete blood count to assess for cytopenias (hemolytic anemia, leukopenia, lymphopenia, thrombocytopenia) 2
• Neurologic manifestations: seizures or psychosis without other cause 2

Additional Serologic Testing

Complement Levels

• Measure C3 and C4 levels, as low complement is characteristic of active SLE and should always be measured alongside anti-dsDNA 1, 3

Specific Extractable Nuclear Antigens (ENA)

• Test for anti-Smith (Sm) antibodies, which are highly specific for SLE even in ANA-negative patients 1, 3
• Test for anti-SSA/Ro and anti-SSB/La antibodies, as these can be present in ANA-negative lupus, particularly subacute cutaneous lupus, neonatal lupus, and Sjögren's syndrome 1, 2
• Test for anti-ribosomal P antibodies if neuropsychiatric symptoms are present 1

Anti-Nucleosome Antibodies

• Consider anti-nucleosome testing, as these antibodies may precede anti-dsDNA in SLE pathogenesis and show 83.33% sensitivity and 96.67% specificity for SLE 1

Antiphospholipid Antibodies

• Test for anticardiolipin, anti-β2-glycoprotein I, and lupus anticoagulant, as 30-40% of SLE patients are positive for antiphospholipid antibodies 1

Interpretation and Management Algorithm

If Anti-DNA is Confirmed Positive and Clinical Suspicion is High:

• Proceed with SLE diagnostic workup using the above clinical and laboratory assessments 1
• Consider that anti-dsDNA antibodies may be detected long before clear clinical signs develop 1
• Establish close clinical follow-up with repeat assessments every 3-6 months 1

If Anti-DNA Cannot be Confirmed (Discordant Results):

• The diagnosis depends fundamentally on clinical characteristics 1
• Recommend repeating anti-dsDNA assays in a new sample 1
• If inconsistency persists, clinical follow-up is warranted as antibodies may fluctuate 1

If Anti-DNA is Confirmed but No Clinical Features Present:

• Do not diagnose SLE based on serology alone, as isolated antibody positivity without clinical manifestations is insufficient 1
• Establish periodic clinical follow-up (every 6 months initially) to monitor for development of symptoms 1
• Educate the patient about warning signs of SLE that should prompt immediate evaluation 1

Common Pitfalls to Avoid

• Do not use ANA for disease monitoring—it is a diagnostic tool only and should not be repeated once positive 1, 3
• Do not dismiss the result as a false positive without confirmation testing, as some patients develop clinical SLE after isolated serologic findings 1
• Do not assume all anti-dsDNA assays are equivalent—method matters significantly, with CLIFT being highly specific but less sensitive than solid-phase assays 1
• Remember that infections (both acute and chronic) can cause positive autoantibody results, so consider and exclude active infections 4
• Be aware that up to 31.7% of healthy individuals can have low-titer positive ANA (1:40), but anti-dsDNA positivity in healthy individuals is rare (0-3%) 5

Special Considerations

• If the patient is asymptomatic with no clinical features of autoimmune disease, the positive anti-DNA may represent a false positive, early/evolving disease, or laboratory error requiring confirmation 1, 5
• The specificity of anti-dsDNA is 97-100% when using appropriate controls, making true positivity clinically significant even without other findings 5
• Different laboratories use different methods and cutoffs, which affects result interpretation—always note the methodology used 1