Use of real time multiplex PCR for the diagnosis of dermatophytes onychomycosis in patients with empirical antifungal treatments

Abstract

Background: Onychomycosis is a nail fungal infection mainly caused by dermatophytes. Diagnostic confirmation is conventionally made by direct microscopy and culture, which suffer from low or moderate sensitivity. Several molecular methods have been used for dermatophytes detection and identification directly from nail samples. The aim of this study was the evaluation of the DermaGenius®(DG) multiplex kit in detecting and identifying dermatophytes from nail samples of untreated and treated patients with a clinical suspicion of onychomycosis.

Methods: All the patients underwent a nail scarification, performed with a sterile scalpel to collect small nail fragments from the suspected site of infection. All nail clippings were first analysed by microscopic and culture methods to define a diagnostic confirmation. DG PCR assays were retrospectively applied to the same samples.

Results: A total of 109 toenails were collected for the microscopic, culture and DG PCR assays. The sensitivity, specificity, positive and negative predictive values of DG in the onychomycosis diagnosis in all 109 patients were respectively 78.5%, 100%, 100%, and 75.9%. Only for cultural exams the rate of positive results was significantly different in the two groups of patients with a percentage of 73.7% in untreated patients versus a 40.7% value in treated patients (P < 0.05).

Conclusions: Our results suggest that the use of DG kit could be useful to confirm the diagnosis of onychomycosis, implementing sensitivity especially in patients who underwent antifungal treatments without any clinical improvement.

Keywords: Dermatophytes; Diagnosis; Multiplex PCR; Onychomycosis.