What is the most sensitive test to use when trying to diagnose toenail fungus? — Keri Lazure, PA-C, Omaha, Neb.
Conventional methods for identifying fungal organisms in the nail plate of patients with onychomycosis (OM) include direct microscopy (after KOH solution incubation), fungal culture, and histopathology (using periodic acid Schiff [PAS] stain).
Surgical pathology testing (of the subungual nail bed and/or the nail plate) using PAS stain is the current gold standard (approaching 100% sensitivity) for the diagnosis of OM.
Newer methods for diagnosing OM include polymerase chain reaction (which has a very high specificity), optical coherence tomography, confocal laser scan microscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and phase contrast hard x-ray microscopy. Confirmation of observations and availability and cost must be considered before these newer methods for diagnosing OM can be incorporated in clinical practice (Indian J Dermatol Venereol Leprol. 2012;78:263-270).— Philip R. Cohen, MD (171-4)
These are letters from practitioners around the country who want to share their clinical problems and successes, observations and pearls with their colleagues. We invite you to participate. If you have a clinical question, submit it here.