Comparative study of direct and indirect immunofluorescence for diagnosis of canine pemphigus foliaceus

ABSTRACT Pemphigus foliaceus (PF) is the most common autoimmune skin disease in dogs. It is characterized by pustules, erosions, and crusts which occur due to the presence of autoantibodies that target intercellular adhesion. Histopathological examination is considered the gold standard pattern in the diagnosis, but may sometimes be inconclusive, especially when the characteristic findings are not identified. New diagnostic tests are continuously being developed and immunofluorescence assays, could be a valuable alternative diagnostic tool. This study aimed to evaluate the applicability of direct and indirect immunofluorescence (DIF and IIF) tests for the diagnosis of canine PF. Twenty eight dogs were divided into two groups: Group I with 14 dogs with PF and Group II (control) with 14 dogs with Superficial pyoderma (differential diagnoses of PF). All animals were submitted to skin biopsy to histopathological and DIF. Blood samples were collected to assess IIF. Comparing the DIF results against the histopathology test, there was an agreement of 75% (9/12) with a Kappa index of 0.77 (P<0.001). Considering IIF, the agreement was 100% (14/14), with a Kappa index of 1.0 (P<0.001). We conclude that DIF and IIF are highly effective and were useful and effective complementary examination tests for an improvement in the diagnosis of canine PF.

摘要 落叶天疱疮（Pemphigus foliaceus, PF）是犬类最常见的自身免疫性皮肤病。该病以脓疱、糜烂及结痂为主要特征，其发病与靶向细胞间黏附的自身抗体存在密切相关。组织病理学检查被公认为该病诊断的金标准，但当未观察到特征性病变时，诊断结果有时会不明确。目前新型诊断方法持续被开发，免疫荧光检测有望成为极具价值的替代诊断工具。本研究旨在评估直接免疫荧光（direct immunofluorescence, DIF）与间接免疫荧光（indirect immunofluorescence, IIF）检测在犬PF诊断中的应用适用性。本研究共纳入28只受试犬，分为两组：组I含14只确诊PF的犬只，组II（对照组）含14只患有浅表脓皮病（PF的鉴别诊断疾病）的犬只。所有受试动物均接受皮肤活检以进行组织病理学检测与DIF检测，同时采集血液样本以开展IIF检测。将DIF检测结果与组织病理学检测结果进行比对，二者诊断一致性达75%（9/12），Kappa指数为0.77（P<0.001）；就IIF检测而言，其与组织病理学检测结果的一致性为100%（14/14），Kappa指数为1.0（P<0.001）。综上，DIF与IIF均具备较高的检测效能，可作为有效的辅助检测手段，助力提升犬PF的诊断水平。