Clin Chem Lab Med. 2026 Mar 5. doi: 10.1515/cclm-2025-1493. Online ahead of print.
ABSTRACT
OBJECTIVES: To determine the prevalence and clinical associations of rare HEp 2 indirect immunofluorescence ANA patterns and to evaluate their relationships with disease categories, ANA titers, and expression form.
METHODS: We retrospectively analyzed 366,524 ANA tests performed between 2018 and 2024 using pattern definitions based on the 2018 ICAP update. Rare patterns were defined as those occurring in less than 1 % of ANA positive cases and represented by more than 30 samples. Clinical diagnoses were categorized as autoimmune, metabolic, infectious, neoplastic, or unclassified.
RESULTS: Among 81,860 ANA positive cases (22.3 %), 1,769 (2.2 %) showed rare patterns. The most frequent rare patterns were AC-22 (0.7 %), AC-23 (0.41 %), AC-25 (0.25 %), AC-26 (0.23 %) and AC-29 (0.16 %). AC-29 was largely confined to autoimmune diseases, particularly systemic sclerosis, and was often observed at high titers. For AC-26, higher titers were more frequently observed among autoimmune disease cases, suggesting titer dependent enrichment. By contrast, AC-22 and AC-23 were more frequently observed in metabolic or infectious diseases and were mainly characterized by low titers (≤1:320). Cytoplasmic and mitotic patterns more commonly appeared as mixed patterns and showed broader distributions across disease categories. Among patients with systemic sclerosis exhibiting the AC-29 pattern, 96.2 % were positive for anti-Scl-70 antibodies.
CONCLUSIONS: Rare ANA patterns show distinct disease and titer profiles. Recognition of these patterns may enhance diagnostic accuracy when interpreted in conjunction with clinical and serological findings.
PMID:41783946 | DOI:10.1515/cclm-2025-1493