GMS is superior to PAS for diagnosis of onychomycosis

Abstract

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. 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. 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. GMS stains are superior to PAS stains for the routine diagnosis of onychomycosis.