Diagnostic Efficacy of Calcofluor White Staining Versus PAS and GMS Staining for Human Sporotrichosis in FFPE Specimens.

OBJECTIVE: This study aimed to evaluate the diagnostic efficacy of calcofluor white (CFW) staining for sporotrichosis using archival formalin-fixed paraffin-embedded (FFPE) specimens, compared with conventional histochemical stains. METHODS: A total of 75 FFPE specimens collected between 2010 and 2023 from patients with culture- or sequencing-confirmed sporotrichosis cases were enrolled, with 70 specimens from non-fungal infection cases using as controls. Serial tissue sections were stained with CFW, periodic acid-Schiff (PAS), and Gomori methenamine silver (GMS) staining, respectively. The detection rates, diagnostic accuracy metrics, and storage duration effects were assessed. RESULTS: CFW staining yielded a fungal detection rate of 78.6% (59/75), which was significantly higher than those of PAS (38.6%, 29/75) and GMS (28.0%, 21/75) (χ2=42.85, P<0.0001) staining. Diagnostic accuracy analysis revealed CFW staining had 78.6% sensitivity, 98.5% specificity, 98.3% positive predictive value, and 81.1% negative predictive value. The fluorescent signal of CFW staining remained stable for at least of 6 months. Additionally, the positive detection rates were not affected by long-term storage (> 10 years: 71.4%; 5-10 years: 70.3%; <5 years: 88.2%; P=0.083). CONCLUSIONS: For archival FEPE specimens, CFW staining exhibits superior sensitivity and excellent specificity for sporotrichosis detection, which enables rapid diagnosis and effectively reduces the risk of misdiagnosis. Considering its technical simple operation, long-term stability, and being compatible with conventional histological examination, CFW staining serves as a valuable adjunctive diagnostic tool, particularly in sporotrichosis- endemic regions. Further prospective multicenter studies were required to validate its clinical application value.