Methods for diagnosing onychomycosis - A comparative study and review of the literature

Objective: To identify the sensitivity of several readily available diagnos tic tests for onychomycosis, Design: Cross-sectional study. Setting: Dermatology and podiatry departments at a teaching hospital. Patients: Sixty-three adult men and women with a clinical examination highl y suggestive of onychomycosis. Main Outcome Measures: Sensitivity of each test and of several test combina tions. Results: Nail samples underwent 6 diagnostic tests. Routine histopathologic examination with periodic acid-Schiff stain (PAS) (PATHPAS) was 85% sensit ive, Sensitivities for potassium hydroxide dissolution and centrifugation c ombined with PAS, fluorescent brightener, or chlorazol black E were 57%, 53 %, and 53%, respectively. Culture on Sabouraud agar with chloramphenicol an d cycloheximide (Mycosel agar) was 32% sensitive; on Littman-oxgall agar, 2 3% sensitive. The most sensitive combination of tests, both culture methods plus PATHPAS, was 94% sensitive (not statistically different from the sens itivity of PATHPAS alone [P=.26]). Conclusions: When onychomycosis is suspected clinically, PATHPAS of the nai l is the single most sensitive of the diagnostic tests we evaluated. Becaus e it is quickly performed and relatively operator independent, PATHPAS is p ractical for clinical and research purposes. Further study is needed to det ermine if sensitivity may be enhanced by combining PATHPAS with cultures ob tained by several collection methods (clipping, curettage, and shaving). Su ch combinations may serve as sensitive and efficient strategies for diagnos ing onychomycosis.