Cathy Rea, MD

Nail plate biopsy followed by periodic acid–Schiff staining is the most accurate method for diagnosing onychomycosis. The positive predictive value (PV+) of periodic acid–Schiff staining was equal to both potassium hydroxide (KOH) preparation and fungal culture, with a greater negative predictive value (PV–) due to superior sensitivity.

However, availability of periodic acid–Schiff staining may vary geographically, and the cost of the diagnostic tests is not addressed in this study. Thus, it makes clinical sense to start with the most accessible test, using periodic acid–Schiff staining if other methods are negative and clinical suspicion is high.

Nail plate biopsy followed by periodic acid–Schiff staining is the most accurate method for diagnosing onychomycosis. The positive predictive value (PV+) of periodic acid–Schiff staining was equal to both potassium hydroxide (KOH) preparation and fungal culture, with a greater negative predictive value (PV–) due to superior sensitivity.

However, availability of periodic acid–Schiff staining may vary geographically, and the cost of the diagnostic tests is not addressed in this study. Thus, it makes clinical sense to start with the most accessible test, using periodic acid–Schiff staining if other methods are negative and clinical suspicion is high.

Nail plate biopsy followed by periodic acid–Schiff staining is the most accurate method for diagnosing onychomycosis. The positive predictive value (PV+) of periodic acid–Schiff staining was equal to both potassium hydroxide (KOH) preparation and fungal culture, with a greater negative predictive value (PV–) due to superior sensitivity.

However, availability of periodic acid–Schiff staining may vary geographically, and the cost of the diagnostic tests is not addressed in this study. Thus, it makes clinical sense to start with the most accessible test, using periodic acid–Schiff staining if other methods are negative and clinical suspicion is high.