Background/Purpose:  The indirect immunofluorescence (IIF) pattern observed in the antinuclear antibody (ANA) test provides an initial assessment of autoantibody responses in candidate patients who have or may be at risk of developing systemic autoimmune rheumatic diseases (SARD). Despite its wide clinical use, a universal nomenclature to describe ANA IIF patterns has not been adopted. The International Consensus on ANA Patterns (ICAP) Initiative originated workshops that began in Sao Paulo (2014), followed by the 2^nd workshop in Dresden (2015). The goal of ICAP is to promote harmonization of ANA pattern nomenclature and provide guidelines for ANA interpretation, thereby optimizing adoption in diagnostic laboratories and extended to patient care.

Methods:  A working committee addressed collective issues on ANA nomenclature that were raised by participants representing research, clinical, and diagnostic laboratories. Post-workshop exchanges were held with the goal of reaching consensus on key issues.

Results:  ANA IIF patterns were separated into three major categories (nuclear, cytoplasmic, and mitotic patterns) and each pattern was defined and described in detail. Consensus was achieved for 28 IIF patterns that were designated with an alpha-numeric code (AC-1 to AC-28) and summarized under a nomenclature and classification tree (ANApatterns.org). Important findings include, e.g., the Homogeneous and Coarse Speckled nuclear patterns are linked to autoantibodies strongly associated with SARD whereas the Dense Fine Speckled (DFS) nuclear pattern in isolation virtually rules out a SARD diagnosis. ICAP initiatives include translation of the website into other languages, establishing guidelines in ANA reporting, and programs for continuing education. The translation initiative promotes the establishment and dynamic engagement of a worldwide network. To date, the website displays its content in English, Spanish, Portuguese, Italian and German while, Chinese, Japanese and French translations are ongoing. Continuous education courses aim to spread and update the ICAP nomenclature/conceptual framework and to promote competency in ANA interpretation.

Conclusion:  ICAP has provided a common platform to address issues that are of great interest to the community. The establishment of a consensus on ANA reporting will require interaction with committees in charge of establishing disease classification and diagnostic criteria. Future goals include building collaborative data on ANA IIF patterns, selection of new consensus patterns, and establishment of an interpretative clinical description for each AC pattern for clinical use. The 3^rd and 4^th ICAP workshops are planned for Kyoto (October 2016) and Dresden (September 2017).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-international-consensus-on-standardized-nomenclature-of-antinuclear-antibody-hep-2-cell-patterns-icap-initiative-update-and-its-impact/