The indirect immunofluorescence assay (IIFA) on HEp- 2 cells is widely used for detection of antinuclear antibodies (ANA).
The dichotomous outcome, negative or positive, is integrated in diagnostic and classification criteria for several systemic autoimmune diseases.
However, the HEp-2 IIFA test has much more to offer: besides the titre or fluorescence intensity, it also provides fluorescence pattern(s).
The latter include the nucleus and the cytoplasm of interphase cells as well as patterns associated with mitotic cells.
The International Consensus on ANA Patterns (ICAP) initiative has previously reached consensus on the nomenclature and definitions of HEp-2 IIFA patterns.
The ICAP consensus describes 29 distinct HEp-2 IIFA patterns (AC-1 to AC-29).
RODS and RINGS PATTERN (AC-23): Most commonly found in HCV patients who have been treated with pegylated interferon-α/ribavirin combination therapy. The HCV patients positive for the AC-23 pattern have been reported to have disease that is more resistant to therapy, but this is not confirmed in other cohorts. The AC-23 pattern has also been reported rarely in individuals without HCV infection, including SLE patients and patients treated with mycophenolic acid, azathioprine, methotrexate or acyclovir, as well as with lower titers in the general population. Specific immunoassays to detect autoantibodies directed to specific Rods and Rings antigens, for instance IMPDH2, are not commercially available.
This clinical relevance is primarily defined within the context of the suspected disease and includes recommendations for follow-up testing.
References
Damoiseaux J, Andrade LEC, Carballo OG, et al. Clinical relevance of HEp-2 indirect immunofluorescent patterns: the International Consensus on ANA patterns (ICAP) perspective. Ann Rheum Dis 2019;78:879–889.
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