Evaluation of a multiplex-PCR-based method for the rapid identification of dermatophytes in nail specimens from patients with suspected onychomycosis

Summary

Onychomycosis is a common nail disorder that can mimic other nail conditions. Fungal infection of the nail requires a long term systemic antifungal treatment, which means that accurate diagnosis is mandatory. The standard procedure for fungal detection in nails requires direct microscopy and culture, but is still time consuming with high rates of false-negative results. Molecular assays offer an alternative diagnostic process that might resolve problems of the standard methodology. The aim of the current study was to evaluate a direct multiplex-PCR method in rapidly identifying dermatophytes in nail specimens. Two-hundred fifty-two nail specimens of clinically suspected onychomycosis cases were prospectively collected and equally divided for direct microscopy, culture and PCR analysis. PCR was performed using the Dermatophyte PCR kit (Statens Serum Institut Diagnostica, Denmark). The whole procedure was completed within 6 hours, including the extraction stage. As many as 86 (34.1%) specimens were PCR-positive for dermatophytes, while 79 (31.3%) were positive by any of the conventional methods (55 by both microscopy and culture, 23 only by microscopic examination, and one only by culture). Thus, by using the PCR assay, the number of positive specimens was increased by 7.1%. Furthermore, the percentage of those with a species-specific identification (Τ. rubrumor dermatophytes) was increased by 11.9% Interestingly, previous treatment uptake was not affecting PCR results since 12 specimens (4 negative with both conventional methods and 8 positive only by microscopy) from patients previously treated with antifungal regimens, were PCR-positive. The findings of this prospective study suggest that this rapid and convenient multiplex-PCR method is a promising complementary diagnostic tool for the management of patients with suspected onychomycosis. (see more)