Onychomycosis diagnostics tools and different approaches

By: Dr. Irit Van-Ham, PhD and CTO of ToeFX

An estimated 10%-20% of the global population suffers from superficial fungal infections, with the number of infected people still increasing . Due to the ubiquity of superficial fungal infections all over the world, our understanding of the causative agents and their pathogenesis has increased thanks to technology.

While superficial human fungal infections are mainly caused by dermatophytes, a fungal etiology accounts for only about 50% of dystrophic nail infections. Clinical diagnosis by an experienced clinician is informative, however supplementation with a laboratory diagnosed dermatophyte infection is advisable to optimize the treatment plan.

The most common etiological agent in onychomycosis is Trichophyton rubrum, followed by Trichophyton mentagrophytes, Trichophyton tonsurans, Epidermophyton floccosum and Trichophyton violaceum, respectively. The key element in the diagnosis of onychomycosis is the collection of an adequate specimen and the correct processing and interpretation of both microscopy and culture results.

Here is a summary of available diagnostics tools and different approaches:

Conventional Diagnostic Tools
• Potassium Hydroxide Testing
Direct potassium hydroxide (KOH) testing is a simple, quick, and inexpensive technique integral to dermatological practice for identifying fungal organisms. KOH dissolves the keratin, allowing microscopic visualization of the fungal septate hyphae. KOH testing has 60-70% sensitivity, is cost-effective, and can determine the presence of fungal organisms within an hour. One drawback is that it is unable to specify the exact type of pathogenic organism.
• Fungal Culture
The Fungal culture test is able to identify specific pathogen(s). Some drawbacks are that sensitivity of fungal culture test is low and largely dependent on the expertise of the testing centre, and requires an adequately sized nail sample. Therefore, a fungal culture test is only recommended when identification of the fungal organism is necessary.

New Diagnostic Tools
• Molecular Assays
Polymerase chain reactions (PCR) is an advanced diagnostic tool that involves analysis of the fungal DNA causing onychomycosis. PCR involves amplification and detection of fungal DNA (similar to COVID testing). It is very sensitive and can detect small amounts of fungal elements within nails.
• Artificial Intelligence
The popularity of Artificial intelligence (AI) is increasing in clinical medicine. The ability of AI to identify disease can, in some instances, be comparable to that of specialist clinicians; examples include diabetic retinopathy and skin cancer.

Onychomycosis is an ideal candidate for AI as it is a common condition, readily identifiable, and easily quantified. Clinics worldwide can contribute to the database, and the AI technology would not be limited to specific populations.
In conclusion, the integration of both conventional and novel diagnostic tools into clinical practice can help clinicians confirm their diagnoses, and therefore maximize the potential of a successful treatment outcome.