Comparison of C3d immunohistochemical staining to ELISA and immunofluorescence for diagnosis of bullous pemphigoid.

Wang LL, Moshiri AS, Novoa R, Simpson CL, Takeshita J, Payne AS, Chu EY

J Amer Acad of Dermatol, 2020. 83(1):172-8. DOI: 10.1016/j.jaad.2020.02.020

PMID: 32068042

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Background: Bullous pemphigoid (BP), the most common autoimmune blistering disease, may be diagnostically challenging. Direct immunofluorescence (DIF), indirect immunofluorescence (IIF), enzyme-linked immunosorbent assay (ELISA), and recently, C3d immunohistochemistry (IHC), are used as adjuncts to diagnosis.

Objective: To compare C3d IHC to DIF, IIF, and ELISA testing in BP diagnosis.

Methods: C3d IHC was performed on skin biopsy specimens from 51 patients (27 with BP and 24 with other blistering diseases) and compared to DIF and IIF, with anti-BP180 or anti-BP230 ELISA results used as the gold standard.

Results: We found C3d IHC, DIF, and IIF had similar sensitivity (74.1%, 63.1%, and 70.4%), specificity (95.8%, 100%, and 100%), positive predictive value (95.2%, 100%, and 100%), and negative predictive value (76.7%, 70.6%, and 75%) for BP. Cases with positive C3d IHC, DIF, and IIF had significantly higher anti-BP180 and anti-BP230 by ELISA than cases with negative testing (P < .0001). False-negative IIF results were associated with lower BP230 compared with true-positive results (P = .03).

Limitations: This was a single-center, retrospective study.

Conclusion: Our study compared C3d IHC to DIF and IIF in BP diagnosis, demonstrating C3d IHC on fixed tissue provides similar diagnostic utility to immunofluorescence and ELISA.

Keywords: C3d immunohistochemistry; ELISA; bullous pemphigoid; diagnosis; direct immunofluorescence; indirect immunofluorescence.

J Amer Acad of Dermatol, 2020. 83(1):172-8. DOI: 10.1016/j.jaad.2020.02.020