Prevalence of autoantibodies to cellular cytoplasmic and mitotic antigens in routine antinuclear antibody reporting: Implementation of international consensus on antinuclear antibodies patterns guidelines

Background: The international consensus on antinuclear antibody (ANA) patterns (ICAP) guidelines recommends that non-nuclear patterns should be reported as positive for ANA. Therefore, a prospective study was planned to investigate the frequency of cytoplasmic and mitotic ANA patterns in routine reporting in a high-throughput lab in a tertiary referral center in Northern India. Materials and Methods: Whole blood samples received were centrifuged and serum was separated within 4 hours of collection. Sera were subjected to indirect immunofluorescence (IIF) assay on HEp-2 cells for ANA determination in a dilution of 1:40, per standardized protocol in our laboratory. IIF staining patterns and intensity were evaluated and the results interpreted. Results: Over a 3-month period, of the 3796 serum samples received for ANA testing, 81 (4.9%) samples were positive for cytoplasmic, 7 (0.4%) for mitotic, and 2 (0.1%) for DNA topoisomerase I (Topo I)-like pattern. The most frequent cytoplasmic fluorescence pattern was dense fine speckled (2%) and the most frequent mitotic pattern was NuMA-like (0.2%). The prevalence of total positive ANA in our study population was found out to be 43.6%. Conclusions: Implementation of ICAP guidelines into routine ANA reporting helped us in detecting important cytoplasmic antibodies such as antimitochondrial antibodies, anti-ribosomal P protein antibodies, anti-Jo-1antibodies, anti-Topo I antibodies and allowed us to introduce more specific and confirmatory tests for the same. The new format for ANA reporting also encouraged clinician-laboratory crosstalk.