BACKGROUND: Onychomycosis is a common cause of deformed nails. Periodic acid-Schiff (PAS) stains are more sensitive than fungal cultures for diagnosing onychomycosis. We performed a retrospective study comparing the use of PAS and Gomori methenamine silver (GMS) stains for histopathologic diagnosis of onychomycosis. METHODS: GMS stains were performed on 20 PAS-positive and 51 PAS-negative cases from nail biopsies with a clinical diagnosis of onychomycosis. The PAS stained slides and GMS stained slides were evaluated for the presence of fungal hyphae. The results were analyzed with McNemar's test. RESULTS: All 20 PAS-positive cases were also positive with GMS stains. Of the 51 PAS-negative cases, GMS stains detected an additional five cases with fungal hyphae. GMS stains were quantitatively superior (p < 0.0253). GMS stains were also qualitatively superior. More fungal hyphae were highlighted and fungal hyphae were more easily recognized on low or medium power magnification. CONCLUSIONS: GMS stains are superior to PAS stains for the routine diagnosis of onychomycosis.
BACKGROUND:Onychomycosis is a common cause of deformed nails. Periodic acid-Schiff (PAS) stains are more sensitive than fungal cultures for diagnosing onychomycosis. We performed a retrospective study comparing the use of PAS and Gomori methenamine silver (GMS) stains for histopathologic diagnosis of onychomycosis. METHODS:GMS stains were performed on 20 PAS-positive and 51 PAS-negative cases from nail biopsies with a clinical diagnosis of onychomycosis. The PAS stained slides and GMS stained slides were evaluated for the presence of fungal hyphae. The results were analyzed with McNemar's test. RESULTS: All 20 PAS-positive cases were also positive with GMS stains. Of the 51 PAS-negative cases, GMS stains detected an additional five cases with fungal hyphae. GMS stains were quantitatively superior (p < 0.0253). GMS stains were also qualitatively superior. More fungal hyphae were highlighted and fungal hyphae were more easily recognized on low or medium power magnification. CONCLUSIONS:GMS stains are superior to PAS stains for the routine diagnosis of onychomycosis.