Diagnostic Utility of BIOCHIP Mosaic Indirect Immunofluorescence in Intraepidermal Autoimmune Blistering Diseases

Background: Pemphigus is a chronic intraepidermal autoimmune blistering disorder (IABD) characterized by the presence of circulating autoantibodies against desmogleins 1and 3. The diagnosis of IABD is a multistep process, combining clinical features, histopathology (HPE), direct immunofluorescence (DIF), indirect immunofluorescence (IIF), enzyme-linked immunosorbent assay, and immunoblotting. Materials and Methods: This was a retrospective cross-sectional study where 121 cases of pemphigus having IIF, HPE and/or DIF tests done and 129 standalone IIF tests were reviewed across a study period of 11 years. Results: We had 121 cases diagnosed as pemphigus on BIOCHIP mosaic IIF with corresponding HPE and/or DIF. For pemphigus vulgaris, the BIOCHIP mosaic IIF showed a sensitivity of 95.29%, specificity and positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 42.85%. For pemphigus foliaceus, BIOCHIP mosaic IIF showed a sensitivity, PPV of 88.88%, and specificity, NPV of 75%. There were also 129 standalone BIOCHIP mosaic IIF tests performed during the study period; clinical concordance was seen in 125 cases (96.8%). Conclusion: BIOCHIP mosaic IIF, when combined with other diagnostic modalities, helps in early diagnosis by enhancing its diagnostic utility and timely management.