Evaluation of the Seegene NovaplexTM dermatophyte assay for diagnosis of onychomycosis.

BACKGROUND

Onychomycosis is a fungal infection of the nails, which can cause significant psychosocial distress. Laboratory confirmation is recommended before initiating treatment.

OBJECTIVE

This study aimed to evaluate the performance of the Seegene NovaplexTM Dermatophyte assay for detecting dermatophyte infections in nail specimens, compared with culture and potassium hydroxide (KOH) smear.

METHODS

149 nail samples submitted for culture and KOH testing were tested on the NovaplexTM Dermatophyte assay. A pre-treatment was developed to optimize the automation of DNA extraction from infected nails. Discrepant samples underwent ITS sequencing to establish a consensus result (agreement of ≥ 2 of 3 methods: culture, PCR, sequencing). Positive and negative percent agreement (PPA/NPA) were calculated versus culture, a composite reference (culture and/or KOH), and consensus. A nail infection model was developed to evaluate rarer clinical isolates. This model was used in analytical studies, including limit of detection (LoD), stability, and interference from topical products.

RESULTS

PPA and NPA for NovaplexTM assay exceeded 95% when compared with culture and composite reference. For Trichophyton rubrum complex, NPA increased from 73% versus culture to 96% versus composite reference and 93% versus consensus. The assay detected an additional 24 TRC and 4 Trichophyton mentagrophytes complex cases missed by culture. Against consensus, PPA and NPA exceeded 99%. Rare clinical isolates were correctly detected in 39/40 cases. Analytical studies confirmed manufacturer LoD, sample stability for up to 12 days, and no interference from topical treatments.

CONCLUSION

The NovaplexTM Dermatophyte assay provides a rapid, accurate, and reliable diagnostic tool for onychomycosis.