Present and potential diagnostic techniques in onychomycosis.

The problem of onychomycosis has been frequently addressed during recent years. To make the diagnosis of onychomycosis dermatologists have relied on clinical presentation, culture, and microscopy. These approaches are hampered by false-negative and false-positive results that have confused treatment outcomes. Two new diagnostic techniques, immunohistochemistry and flow cytometry, provide an effective means of identifying different dermatophytes, yeasts, and nondermatophytic molds. Immunohistochemistry employs antibodies to certain fungi to enable positive identification in situ, whereas flow cytometry differentiates fungi on the basis of molecular differences. These techniques provide new evidence that nondermatophytic molds and yeasts can actively invade nail tissue and that mixed infections occur. These findings could have important implications for the treatment of onychomycosis.