Sensitivity of ANA in SLE
The sensitivity of ANA testing for SLE is approximately 100%, making it an excellent screening test to rule out the disease. 1, 2
Diagnostic Performance Characteristics
ANA testing demonstrates nearly 100% sensitivity for SLE, meaning a negative ANA effectively excludes the diagnosis in the vast majority of cases 1, 2
The high sensitivity comes at the cost of low specificity—ANA can be positive in numerous other autoimmune conditions, infections, and even healthy individuals (31.7% at 1:40 dilution, 13.3% at 1:80, and 5.0% at 1:160) 3
At a screening dilution of 1:160, ANA maintains 95.8% sensitivity while achieving 86.2% specificity for systemic autoimmune rheumatic diseases, representing the optimal balance for clinical use 3
Clinical Implications of High Sensitivity
Because of its near-perfect sensitivity, ANA serves as the best screening assay for ruling out SLE—a negative result makes the diagnosis highly unlikely 1
The test should be performed using indirect immunofluorescence on HEp-2 cells, which remains the reference standard method 2
ANA positivity alone cannot confirm SLE due to poor specificity; diagnosis requires compatible clinical symptoms plus specific autoantibodies like anti-dsDNA or anti-Sm 3, 1
Important Caveats
Rare ANA-negative SLE cases can occur, particularly when specific autoantibodies like anti-SSA/Ro, anti-ribosomal P, or anti-Jo-1 are present but not detected by standard immunofluorescence 3
In cases of high clinical suspicion, specific antibody testing should be pursued regardless of ANA result 3
ANA testing is intended for diagnostic purposes only and should never be repeated for monitoring disease activity once a diagnosis is established 3, 4