Comparison of diagnostic methods for onychomycosis, and proposal of a diagnostic algorithm.

Abstract

BACKGROUND:

Traditionally, the gold standard for diagnosis of onychomycosis has been the combination of direct microscopy with potassium hydroxide (KOH) staining and fungal culture. However, several studies have suggested that periodic-acid-Schiff (PAS) staining of nail-plate clippings may be a very sensitive method for the diagnosis of onychomycosis.

AIM:

To compare the sensitivities of direct microscopy with KOH, fungal culture and PAS staining of nail-plate clippings, and to define an efficient, high-yield and cost-effective diagnostic strategy for the diagnosis of onychomycosis in the clinical setting.

METHODS:

We evaluated a total of 493 patients with clinically suspected onychomycosis. Group A comprised 400 patient samples, evaluated using fungal culture and PAS stain, while group B comprised 93 patient samples evaluated using KOH, fungal culture and PAS. Diagnosis of onychomycosis was defined as clinical morphology plus at least one positive test result.

RESULTS:

In group A, sensitivities of fungal culture and PAS were 49.5% and 93.1% (P < 0.005), respectively. In group B, the most sensitive single test was PAS (88.2%) followed by KOH (55.9%) and fungal culture (29.4%). The combination of fungal culture and PAS (94.1%) was significantly (P < 0.001) more sensitive than that of KOH and culture (72.1%).

CONCLUSION:

PAS staining of nail clippings is much more sensitive than KOH and fungal culture for the diagnosis of onychomycosis. Based on our results, we propose a diagnostic algorithm for onychomycosis that takes into consideration the sensitivity, cost-effectiveness and necessary time for each test.

• Authors: M Y Jung, J H Shim, J H Lee, J H Lee, J M Yang, D-Y Lee, K-T Jang, N Y Lee, J-H Lee, J-H Park, K K Park
• Journal: Clinical and experimental dermatology (Clin Exp Dermatol) Vol. 40 Issue 5 Pg. 479-84 (Jul 2015) ISSN: 1365-2230 [Electronic] England
• PMID: 25683452 (Publication Type: Journal Article)
• Copyright: © 2015 British Association of Dermatologists.

Chemical References

• Fluorescent Dyes
• Hydroxides
• Indicators and Reagents
• Potassium Compounds
• potassium hydroxide

Topics

• Adult
• Aged
• Algorithms
• Female
• Fluorescent Dyes
• Foot Dermatoses (diagnosis, microbiology)
• Fungi (isolation & purification)
• Hand Dermatoses (diagnosis, microbiology)
• Humans
• Hydroxides
• Indicators and Reagents
• Male
• Microscopy (methods)
• Middle Aged
• Mycology (methods)
• Onychomycosis (diagnosis, microbiology)
• Periodic Acid-Schiff Reaction
• Potassium Compounds
• Predictive Value of Tests
• Sensitivity and Specificity
• Staining and Labeling (methods)