Scoping Review Highlights Diagnostic Value of Direct Immunofluorescence in Cutaneous Vasculitis

The review, published in the Journal of Cutaneous Pathology emphasizes that DIF testing plays a crucial role not only in confirming a diagnosis of vasculitis but also in classifying disease subtypes and predicting potential systemic associations.

Cutaneous vasculitis can manifest in various ways, leading to skin lesions that may mimic other dermatological conditions. Accurate diagnosis is vital, as the treatment and management of vasculitis can differ significantly from other skin disorders.

Given the immune-mediated nature of non-infectious cutaneous vasculitis, skin biopsy samples are frequently sent for DIF testing when vasculitis is suspected clinically. However, the clinical significance of DIF testing has not been thoroughly evaluated in the existing literature. To fill this knowledge gap, Julia S Lehman, Department of Dermatology, Mayo Clinic, Rochester, Minnesota, USA, and colleagues systematically assessed the peer-reviewed literature on the utility of DIF in vasculitis to help inform the development of appropriate use criteria by the American Society of Dermatopathology.

For this purpose, the researchers searched two electronic databases for articles on direct immunofluorescence (DIF) and vasculitis, covering the period from January 1975 to October 2023. They included relevant case series featuring three or more patients, published in English, and available in full text. Additional articles were identified through manual reference review. Given the heterogeneity of the studies, the findings were analyzed descriptively.

The key findings were as follows:

• Out of 255 articles identified, 61 met the inclusion criteria, collectively representing over 1,000 DIF specimens.
• Several studies estimated the sensitivity of DIF to be around 75%.
• Vascular immunoglobulin A (IgA) deposits identified by DIF were linked to renal disease, while other systemic associations varied.
• Vascular IgG deposition may be more prevalent in ANCA-associated vasculitis.
• The presence of granular vascular and epidermal basement membrane zone immunoglobulin deposition was able to differentiate between hypocomplementemic and normocomplementemic urticarial vasculitis. However, few studies have explored the added value of DIF compared to routine microscopy alone in vasculitis.

"The use of DIF testing, along with biopsy and hematoxylin and eosin staining, continues to be a cornerstone of the gold standard work-up for diagnosing vasculitis. This is particularly true for IgA vasculitis, where IgA deposits are closely linked to an increased risk of renal disease," the researchers wrote.

"Further studies are needed to compare the sensitivity of DIF testing with that of histopathology," they concluded.

Reference:

Lehman JS, Ferringer TC, Fung MA, Cassarino DS, Shalin SC. Diagnostic utility of direct immunofluorescence test panels for cutaneous vasculitis: A scoping review. J Cutan Pathol. 2024 Sep 22. doi: 10.1111/cup.14722. Epub ahead of print. PMID: 39307568.