A Comparative Study of KOH Preparation, Fungal Culture, Histopathologic Examination and Polymerase Chain Reaction for Diagnosis in Onychomycosis

Shin, Young Min; Shin, Dong Hoon; Choi, Jong Soo; Kim, Ki Hong; Kim, Geuk Jun

Abstract

BACKGROUND: Onychomycosis is one of the most common nail disorders, and it is necessary of mycologic confirmation to treat correctly. It has been reported that histopathologic evaluation and polymerase chain reaction (PCR) of the nail plate by nail clipping might be a useful supportive method for identification of causative fungi showing higher detection rates.
Objective
This study was designed to compare diagnostic efficacy of KOH preparation, fungal culture, histopathologic examination and PCR in onychomycosis.
METHODS
Using 60 nail samples from 60 patients with clinically suspected onychomycosis, KOH preparation and fungal culture with nail and subungual tissue was performed. And histopathologic examination with PAS staining and PCR with DNA extracted from paraffin block was performed.
RESULTS
The results are summarized as follows: 1. The positive rates of conventional KOH preparation, fungal culture, histopathologic examination and PCR were 87.5%, 8.9%, 87.5% and 83.9%. 2. In histopathologic examination, fungi were distinguished as 3 groups based on Kim and Cho's classification (1997): dermatophytes, Candida sp. and non-dermatophytic mold (NDM). Fifteen of 49 samples are dermatophytes, 1 is Candida sp., and 7 are NDM, 8 are dermatophytes and Candida sp. mixed infections, 18 are dermatophytes and NDM mixed infections. 3. In PCR, 1 of 47 samples is Trichophyton rubrum, 4 are Candida sp. and 39 samples are NDM.
CONCLUSION
Histopathologic examination in onychomycosis is considered to be an useful supportive method in diagnosis and identification of causative fungi in onychomycosis.