Antinuclear Antibodies in Uveitis

Antinuclear antibodies (ANA) are autoantibodies directed against nuclear, nucleolar, or perinuclear antigens, serving as hallmark markers for various autoimmune disorders. While their precise pathogenic mechanism remains unclear, ANA presence is most clinically relevant when detected in high, persistent titers alongside distinct systemic symptoms. (1)

The diagnostic utility of ANA is enhanced by identifying specific antibodies against extractable nuclear antigens (ENA), which correlate with distinct clinical phenotypes:
Anti-Ro/SSA and Anti-La/SSB: These are highly associated with specific systemic manifestations; notably, over 90% of anti-Ro-positive patients report photosensitivity, often leading to cutaneous rashes.
Anti-dsDNA: Highly specific for Systemic Lupus Erythematosus (SLE), these antibodies are present in approximately 50% of patients at diagnosis. Their prevalence increases significantly, up to 80–90%, in patients with severe disease, particularly those presenting with glomerulonephritis.

Clinical Pearls for Ophthalmologists:
   •   Avoid Routine Screening: Do not order ANA as a routine “pan-uveitis” panel for all patients. It is most useful only when there is high clinical suspicion of a systemic rheumatic disease. (2) (3)
   •   Pediatric Exception: ANA testing remains a standard, essential part of the diagnostic work-up for children under 16 years, primarily to assess the risk of JIA-associated uveitis. (3) (4)
   •   Look for Systemic “Red Flags”: Reserve testing for patients presenting with systemic signs (e.g., malar rash, symmetric polyarthritis, or unexplained nephritis) or specific ocular findings like scleritis or retinal vasculitis that suggest a systemic autoimmune process.
   •   Interpret Titers Cautiously: A low-titer positive (e.g., 1:40 or 1:80) in an otherwise healthy or asymptomatic patient is frequently a non-specific finding. High titers (e.g., ≥1:320) are more likely to be clinically significant.
   •   Order Reflexive Testing: If an ANA result is positive, do not stop there. Reflexive testing for specific autoantibodies (e.g., anti-dsDNA, anti-Ro/SSA, anti-La/SSB) is necessary to confirm or rule out specific systemic autoimmune diseases.

Understanding Dilution and Antibody Strength of ANA:

The “titer” in an ANA test measures the concentration of antibodies by determining the highest level of dilution at which these antibodies remain detectable in your blood sample. The process of serial dilution works like concentrating a liquid; each step (e.g., from 1:40 to 1:80 to 1:160) involves halving the concentration of the original serum.

If a laboratory finds a positive result at 1:40, they further dilute the serum to 1:80. If it is still positive, they proceed to 1:160, 1:320, and so on.
The higher the dilution ratio (e.g., 1:640 vs. 1:40), the more antibodies were present in the initial sample. A result that remains positive at 1:320 means that even after diluting the original serum 320 times, enough antibodies remain to be detected by the microscope.
Consequently, higher titers indicate a higher concentration of autoantibodies, which correlates more strongly with clinically active systemic autoimmune disease. Conversely, low-titer positives (1:40 or 1:80) often represent low-level, non-specific findings that can be seen in perfectly healthy individuals.

Dilution Ratio	Interpretation	Clinical Significance	Estimated Prevalence in Healthy Individuals
1:40 – 1:80	Low Positive	Often non-specific; common in healthy populations	~30% – 32%, 1: 18~13%
1:160	Moderate Positive	Intermediate; requires strong clinical correlation	~5%
1:320	High Positive	Strong indicator; high association with systemic disease	~3% – 6%
≥ 1:640	Very High Positive	Often points to active systemic pathology

References:

1. Swaak AJ, Groenwold J, Aarden LA, Statius van Eps LW, Feltkamp EW. Prognostic value of anti-dsDNA in SLE. Ann Rheum Dis. 1982 Aug;41(4):388-95.

2. Ten Berge JC, Groen-Hakan F, Rothova A, Schreurs MWJ. Antinuclear antibody profiling in uveitis. Acta Ophthalmol. 2018 Aug;96(5):e660-e661.

3. Rathinam SR, Tugal-Tutkun I, Agarwal M, Rajesh V, Egriparmak M, Patnaik G. Immunological tests and their interpretation in uveitis. Indian J Ophthalmol. 2020 Sep;68(9):1737-1748.

4. Majumder PD, Sudharshan S, Biswas J. Laboratory support in the diagnosis of uveitis. Indian J Ophthalmol. 2013 Jun;61(6):269-76.

5. Grygiel-Górniak B, Rogacka N, Puszczewicz M. Antinuclear antibodies in healthy people and non-rheumatic diseases - diagnostic and clinical implications. Reumatologia. 2018;56(4):243-248.