What does the Antinuclear Antibody Screen test measure?

Why is Antinuclear Antibody Screen measured?

The ANA is the gatekeeper test for systemic lupus erythematosus and other connective-tissue diseases. A negative screen has high negative predictive value and effectively rules out active SLE, but a positive result is non-specific — it must be interpreted by titre, pattern, clinical context, and follow-on extractable nuclear antigen serology. Titre correlates loosely with disease likelihood, and the fluorescence pattern guides selection of confirmatory antibodies.

Reference ranges

Standard reference

Negative at 1:40 dilution. Positive results are reflexed to titre and fluorescence pattern.

Functional medicine optimal

Negative. Low-titre positivity without clinical features does not require intervention; high titres (≥1:160–1:320) warrant reflex antigen-specific testing and rheumatology assessment when clinical suspicion is present.

Units

Titre (≥1:40, 1:80, etc.), Pattern (homogeneous, speckled, nucleolar, centromere), qualitative (positive/negative), titre (1:40, 1:80, 1:160, 1:320, ≥1:640)

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.