Rare Antinuclear Antibody Patterns: Relevance in Routine Laboratory Reporting

Introduction: Uncommon patterns on Human Epithelial 2 (Hep 2) substrate during Antinuclear Antibody (ANA) screening by Indirect Immunofluorescence (IIF) microscopy are not routinely reported by many laboratories since their clinical relevance is not well established. Aim: To elucidate rare ANA patterns on Hep 2 and their possible association with clinical presentation. Materials and Methods: A retrospective study was conducted on ANA reports in the duration January 2021 to March 2022 at the Department of Laboratory Medicine, Dr. Sulaiman Al Habib Medical Group, Olaya Medical Complex, Riyadh, Saudi Arabia, to recognise rare ANA patterns. Gold standard method of IIF on Hep 2 was used for screening. Statistical evaluation was done to obtain frequencies of various ANA patterns. Those with frequency of less than 1% were classified as rare patterns. Results: Overall, 4207 consecutive ANA reports were evaluated out of which 1388 were positive and 210 (4.99%) demonstrated rare ANA patterns including nuclear, cytoplasmic and mitotic subtypes. Most commonly encountered among the rare ANA patterns was intercellular bridge (AC 27) with frequency of 0.78% (n=33). Systemic Lupus Erythematosus (SLE) (10/210) was the most often observed clinical association with rare cytoplasmic and mitotic patterns at titer ≥1:160. Conclusion: Uncommon ANA patterns may be useful in initial work-up of autoimmune illness hence, should be routinely reported. Further studies to enlighten the significance of these patterns, analogous antibodies could be of diagnostic relevance in autoimmune and other diseases.