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Fungal nail infection (onychomycosis) - Management
How should I confirm fungal nail infection?
- To confirm the diagnosis, send specimens of nail clippings or scrapings for fungal microscopy and culture.
- Testing for infection is not needed if treatment would not be given — see Decision to treat.
- Microscopy results should be available within a few days, but culture results may take 4–6 weeks.
- The results are regarded as positive:
- For dermatophytes, if either microscopy or culture is positive.
- For Candida species, if both microscopy and culture are positive.
- For non-dermatophytes if both microscopy and culture are positive on at least two samples taken at different times.
- Non-dermatophyte moulds are rare causes of nail infection. They usually colonize nails as a secondary infection following trauma or an underlying dermatophyte infection.
- False-negative rates are high (about 30%). Therefore:
- A negative test cannot definitively exclude fungal nail infection.
- Repeat the test if the result is negative, and there is high clinical suspicion that the nail is infected.
- Testing for antifungal susceptibilities is not required.
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