To determine the cause of a nail
problem and diagnose a
fungal nail infection, your doctor:
Will ask about your medical history, including any previous
symptoms of nail damage or fungal nail infections.
Will look at the skin and nails on your hands and feet.
May take a sample of the bits of skin and nail fragments (debris)
from under the infected nail. If a sample of debris can't be taken easily, a
nail sample may be taken by lightly scraping the nail near the infected area or
by using a small blade to shave off a piece of nail.
Tests used to examine nail and debris samples
fungal culture. This can show which type of
fungus is present. Fungi typically grow slowly, so it can take several weeks
for a culture to produce test results.
Almost all fungal toenail infections are caused by a type
of fungus called a dermatophyte. Because of this, if
the KOH test shows that there's a fungus present, your doctor may assume that the
infection is caused by a dermatophyte and prescribe treatment. But
because one medicine may work better than another medicine against
certain types of fungus, your doctor may want to do a fungal culture.
Your doctor may
remove a small piece of nail and look at it under a microscope (nail
biopsy) if the KOH preparation and fungal culture do not show the
presence of fungi but a fungal infection is still suspected.