Comparison of Diagnostic Methods in the Evaluation of Onychomycosis

Abstract

Onychomycosis is a common nail problem, accounting for up to half of all nail diseases. Several nail disorders may mimic the onychomycosis clinically. Therefore, a sensitive, quick, and inexpensive test is essential for screening nail specimens for the administration of the proper drug. The aim of this study was to compare 4 different diagnostic methods in the evaluation of onychomycosis and to determine their sensitivity, specificity, positive predictive value, and negative predictive value. In a cross-sectional study, nail specimens were collected from 101 patients suspected to have onychomycosis during a 14-month period. The nail specimens were examined using potassium hydroxide (KOH) 20 %, KOH-treated nail clipping stained with periodic acid-Schiff (KONCPA), and calcofluor white (CFW) stain, and grew a fungal culture. The culture was chosen as the gold standard for statistical analysis using the McNemar and chi-square tests. Out of 101 patients, 100 (99 %) patients had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The positive rates for the fungal culture, KOH preparation, CFW, and KONCPA were 74.2, 85.1, 91.09, and 99.01 %, respectively. The sensitivity and negative predictive value of KONCPA was 100 %. KONCPA was the most sensitive among the tests and was also superior to other methods in its negative predictive value. KONCPA was easy to perform, rapid, and gave significantly higher rates of detection of onychomycosis compared to the standard methods of KOH preparation and fungal culture. Therefore, KONCPA should be the single method of choice for the evaluation of onychomycosis.

Non-dermatophytic moulds and yeasts as agents of onychomycosis in a Malaysian medical centre

“…Onychomycosis (plural: onychomycoses) is a common condition, making up approximately half of all nail disorders 1 . Dermatophytes have previously been reported to be the dominant aetiological agents in onychomycosis 1,2 .…”

“…Dermatophytes have previously been reported to be the dominant aetiological agents in onychomycosis 1,2 . All three dermatophyte genera (Trichophyton, Epidermophyton and Microsporum) are implicated in onychomycosis.…”

Cost-effectiveness of Confirmatory Testing Before Treatment of Onychomycosis

“…the high prevalence (99%) of onychomycosis in the trial by Haghani et al 14 The test statistics from Weinberg et al demonstrated in-clinic KOH sensitivity and specificity values of 80% and 72%, respectively, and PAS sensitivity and specificity values of 92% and 72%, respectively. Given the lack of data regarding the effect of KOH testing on sequential PAS testing, we assumed in our model that the performance of PAS was independent of KOH results.…”

“…Models 2 and 3 were chosen based on multiple studies and international guidelines that recommend the use of PAS for out-of-office testing and in-clinic KOH screening as the least costly, most broadly available in-office procedure. 1,5,[11][12][13][14][15][16] Assigning Cost and Classification Probabilities…”

“…Only 2 prospective studies 13,14 included outcome data for the sensitivity and specificity of both diagnostic tests. The present study used test statistics from the trial by Weinberg et al 13 given…”