Clinical Usefulness of PCR-REBA for Diagnosis of Onychomycosis

Kim, Joon Goon; Shin, Dong Hoon; Choi, Jong Soo; Lee, Chae Hoon

Abstract

BACKGROUND
PCR-based reverse blot hybridization assay (PCR-REBA) has high sensitivity and specificity, can be performed directly on nail samples, is relatively cheaper than other molecular biologic methods, and is useful for diagnosing onychomycosis.
OBJECTIVE
This study aims to compare the diagnostic efficacy of fungal culture and REBA Fungus-ID® which is a commercial PCR-REBA-based kit used for onychomycosis diagnosis.
METHODS
Fifty nail samples were collected from 50 patients diagnosed with onychomycosis via direct microscopic examination using KOH preparation, and subjected to fungal culture and REBA Fungus-ID® test.
RESULTS
The sensitivity of conventional fungal culture and REBA Fungus-ID® was 56% and 100%, respectively. In REBA Fungus-ID®, 43 of 50 samples were found to be infected with Trichophyton rubrum. Four of the remaining 7 samples were identified as infected with Trichophyton spp., one with Trichophyton mentagrophytes, and two revealed a panfungal DNA sequence. In fungal culture, 28 of 50 samples showed growth, of which 18 samples were identified as T. rubrum, 3 as Rhodotorula mucilaginosa, 3 as Cladosporium spp., 1 as Cyphellophora europaea, 1 as Penicillium cvjetkovicii, 1 as Lachnum soppittii, and 1 as non-dermatophytic mold. REBA Fungus-ID® and fungal culture were identical in 20 cases (40%). The non-dermatophytic fungi identified in fungal culture were considered contaminants.
CONCLUSION
Nail specimens can be used directly for REBA Fungus-ID®, which has a high sensitivity for onychomycosis diagnosis. Therefore, it can be considered useful for diagnosis and identification of the causative organism in mixed infections like onychomycosis.