Frequency of the AC-2 pattern's new variant (AC-30) and detection of different immunological relationships

This study investigates the frequency and autoantibody profile of the newly defined AC-30 pattern, a variant of the AC-2 dense fine speckled pattern, in patients undergoing antinuclear antibodies (ANA) testing via IIF on HEp-2 cells.

A total of 12,369 samples collected between July 2024 and March 2025 were retrospectively analyzed. Upon re-evaluation, 147 samples (8.78 %) were identified as AC-30. The most common patterns were speckled (29.25 %), dense fine speckled (25.25 %), homogeneous (10.99 %), and AC-30 (8.78 %). Extractable nuclear antigen (ENA) analysis showed that 68.7 % of AC-30 samples were negative, while 31.3 % were positive most frequently for anti-DFS70, anti-dsDNA, anti-PM/Scl, and anti-SSA/Ro60.

Accurate identification of the AC-30 pattern is essential to prevent misclassification as AC-1 or AC-2, which may lead to diagnostic errors. Further multicenter studies are needed to clarify the clinical relevance and diagnostic value of the AC-30 pattern.