Background: Pemphigus is identified by the intercellular deposition of immunoglobulin IgG on direct immunofluorescence (DIF) within skin, hair follicles, and oral mucosa. The objective of this study was to evaluate the diagnostic accuracy of DIF in hair, oral mucosal scrapes, and Tzanck smears, with DIF of skin serving as the reference standard.
Materials and methods: This cross-sectional observational study included patients with clinically suspected pemphigus (n=70) selected through non-probability sampling and compared them with age-matched controls (n=70) who had non-pemphigus bullous lesions. All participants underwent Direct Immunofluorescence (DIF) of hair, oral mucosal scrapes, and Tzanck smears following histopathological examination. The sensitivity, specificity, diagnostic accuracy, and area under the receiver operating characteristic curve (ROC) were calculated.
Results: Of the 70 clinically suspected cases of pemphigus, histopathology confirmed 64 cases (91.4%) as pemphigus vulgaris and 6 cases (8.6%) as pemphigus foliaceus. Perilesional skin biopsy showed a fish net pattern (intercellular IgG deposition) in 100% of pemphigus cases. DIF of the outer root sheath of scalp anagen hair demonstrated this pattern in 94.3% of cases. Tzanck smears from fresh blisters showed pericellular membranous deposits on acantholytic cells in 69.3% of cases. Oral scrapes DIF indicated pericellular deposition around acantholytic cells in 65.7% of cases. Controls (n=4) also exhibited IgG intercellular deposition (fish net pattern) on DIF. ROC curve analysis revealed that hair DIF had a superior diagnostic accuracy (AUC = 0.968), compared to oral scrapes DIF (AUC=0.917) and Tzanck smear DIF (AUC=0.771), respectively.
Conclusion: DIF analysis of hair has superior diagnostic accuracy as compared to oral and tzanck smear.