Methods for diagnosing onychomycosis: A comparative study of 459 cases

Background: Onychomycosis is a common infectious nail problem but shares similar clinical presentation with some other noninfectious disorders, such as psoriasis and lichen planus. A correct diagnosis is essential to proper management. There are three common tests used in the outpatient clinic, including direct potassium hydroxide (KOH) examination, nail plate histology study, and fungal culture. Objective: This study aimed to compare the accuracy and feasibility among these three tests in the diagnosis of onychomycosis. Materials and Methods: We retrospectively reviewed the patients diagnosed with onychomycosis and had positive result of any of the three tests from June 2005 to June 2015. The age, gender, and results of the diagnostic methods were collected and analyzed. Results: A total of 459 patients were enrolled. The positive rates were significantly different between nail plate histology study (93.0%, 427/459), KOH examination (67.3%, 309/459), and fungal culture (42.1%, 193/459) (P < 0.05). Conclusions: Nail plate histology study has the highest positive rate in the diagnosis of onychomycosis than KOH examination and fungal culture. However, KOH examination is most inexpensive and is the fast way to obtain the result with moderate reliability. A combination of two or three diagnostic tests could provide useful information to the clinician to manage onychomycosis appropriately.