What does the Anti-Chromatin (Nucleosome) Antibody test measure?

Why is Anti-Chromatin (Nucleosome) Antibody measured?

Anti-chromatin is found in 50–80% of SLE cases and is included as a weighted biomarker domain in the 2019 EULAR/ACR SLE classification criteria, providing additive diagnostic sensitivity alongside anti-dsDNA, particularly in anti-dsDNA-negative patients. It is also associated with drug-induced lupus; serial monitoring has limited utility as titres do not consistently track disease activity.

Reference ranges

Standard reference

<1.0 AI (negative); ≥1.0 AI (positive) # REVIEWER FLAG: Confirm cut-off and reporting format with Access Med Labs.

Functional medicine optimal

Negative — positive result contributes to EULAR/ACR SLE classification scoring and should be interpreted alongside anti-dsDNA and clinical criteria.

Units

AI (antibody index)

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