Abstract

Background: Dermatologists submit direct immunofluorescence (DIF) biopsies on a daily basis, employing an assay detecting immunoreactant deposition using a panel that has traditionally been comprised of IgG, IgA, IgM, C3, fibrin, +/- albumin antibodies. Objective: To better understand the need to utilize the full antibody panel on all DIF biopsies, and to assess the use of DIF biopsies by dermatologists in the work up of cutaneous diseases, we performed a quality improvement study to evaluate and compare the frequency of immunoreactants in DIF biopsies submitted over an 8 year period and to assess the pattern of use by dermatologists based on clinical impression. Methods: Results of consecutive DIF skin biopsies submitted to our laboratory between 2012-2020 were analyzed by final pathologic diagnosis and antibody subtype positivity, in comparison to clinical impression. Results: Of 2,050 DIF biopsies submitted, 372 (18%) were positive. IgG, IgA, and C3 alone identified all primary immunobullous disease cases (pemphigoid, pemphigus, linear IgA, and dermatitis herpetiformis). IgA, C3, and fibrin antibodies alone identified all vasculitis cases. A panel of IgG, IgA, IgM, and fibrin identified all cases of lupus erythematosus (LE). DIF was positive in less than half of cases of H&E biopsy-confirmed LE (23/47). 247 biopsies were submitted for clinical diagnoses not optimally supported on DIF - lichen planus, porphyria, and connective tissue disease. Conclusion and Relevance: A knowledge gap exists among dermatologists relating to appropriate use of DIF. The practice of reflexive antibody testing employing a 6-antibody panel for all DIF biopsies is unnecessary. DIF protocols tailored to the clinical diagnosis will enhance cost-effectiveness without loss of test sensitivity or specificity.

Financial Disclosure: No current or relevant financial relationships exist.