What does the Antinuclear Antibody test measure?

Why is Antinuclear Antibody measured?

The ANA screen is the principal first-line test for suspected systemic autoimmune disease, particularly systemic lupus erythematosus, for which it is highly sensitive. Because it is not specific and a low-titre positive is common in healthy people, a positive result is interpreted in the clinical context and followed by specific antibody testing (such as anti-dsDNA, anti-Sm, anti-Ro/La, anti-centromere, anti-Scl-70) guided by the titre and pattern. A negative ANA makes SLE unlikely but does not exclude all autoimmune disease.

Reference ranges

Standard reference

Negative; positives reported with a titre (e.g. 1:40, 1:80, 1:160, 1:320) and, by immunofluorescence, a staining pattern # REVIEWER FLAG: Positivity threshold, titre reporting, and whether the screen is by indirect immunofluorescence (IFA) or immunoassay are method-dependent — reviewer to confirm against Access Medical Laboratories' methodology and cut-off.

Functional medicine optimal

A negative result is the expected normal; there is no target titre above negative

Units

titre, positive/negative

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