Onychomycosis laboratory findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Laboratory findings consistent with the diagnosis of onychomycosis include potassium hydroxide smear, culture and histology.

If all nails are affected then fungal infection is improbable. To avoid misdiagnosis as psoriasis, lichen planus, contact dermatitis, trauma, nail bed tumor or yellow nail syndrome, laboratory confirmation may be necessary. The three main approaches are potassium hydroxide smear, culture and histology. This involves microscopic examination and culture of nail scrapings or clippings. Recent results indicate that the most sensitive diagnostic approaches are direct smear combined with histological examination^[1] and nail plate biopsy using periodic acid-Schiff stain^[2].