Background: Antinuclear antibodies (ANA) detected by indirect immunofluorescence assay (IFA) on HEp-2 cells are important for the diagnosis of systemic rheumatic diseases. ANA is an entry criterion in the 2019 classification criteria for systemic lupus erythematosus (SLE). The International Consensus on ANA Patterns (ICAP) and computer-aided immunofluorescence microscopy (CAIFM) and have been introduced for ANA interpretation. This study aimed investigate the status of ANA testing in Korea.
Methods: The study conducted an e-mail survey in July 2019. The survey containing 15 items were emailed to 49 clinical pathologists at 42 tertiary referral hospitals and seven reference laboratories. A total of 37 pathologists replied (response rate: 75.5%). Statistical analysis was performed based on the responses from 36 institutions because one hospital did not perform ANA testing.
Results: All the laboratories performed ANA testing by IFA on Hep-2 cells. Of these, 21 laboratories (58%) used 1:40 as the screening dilution titer, while the titer of final dilution varied. Ten of 12 laboratories using CAIFM applied it to negative/positive determination, and 59% (n=12 laboratories) used it for reading the fluorescence pattern. Moreover, 33 clinical pathologists (92%) who was familiar with ICAP responded. Furthermore, 33 laboratories (92%) responded that they do not use the anti-cell (AC) code, while 16 laboratories (48%) indicated an intention to use the AC code.
Conclusions: The use of 1:40 dilution screening titer for the diagnosis of SLE in laboratories needs to be considered. The findings of this study may be used to better inform standardized ANA reporting and for establishing the Korean ANA reporting guidelines.

Keywords: Antinuclear antibody, International Consensus on ANA Patterns, HEp-2 cell, Immunofluorescence assay, Korea