Modified PAS stain: A new diagnostic method for onychomycosis

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• 作者：Tamar Hajar^a ; ^{hajar@ohsu.edu" class="auth_mail" title="E-mail the corresponding author} ; Ramon Ferná ; ndez-Martí ; nez^b ; Gabriela Moreno-Coutiñ ; o^b ; Elsa Vá ; squez del Mercado^b ; Roberto Arenas^c
• 关键词：Mycology ; Diagnosis ; Onychomycosis
• 刊名：Revista Iberoamericana de Micología
• 出版年：2016
• 出版时间：January-March 2016
• 年：2016
• 卷：33
• 期：1
• 页码：34-37
• 全文大小：499 K

文摘

Onychomycosis is the most common nail disease and represents around 50% of nail disorders. Accurate diagnosis with adequate evidence is ideal before starting any treatment. Current diagnostic methods offer low specificity and sensitivity.

Aims

To create a new method for the diagnosis of onychomycosis, and to compare its sensitivity and specificity with the existing methods.

Methods

One hundred and ninety-two samples with clinical suspicion of onychomycosis were included and underwent modified PAS stain (M-PAS), KOH/chlorazol black (KOH/CB) and culture testing. Sensitivity, specificity, positive and negative predictive values were calculated.

Results

In 152 out of 192 samples (79.2%) fungi structures were found in at least one of the three tests performed, and the patients were diagnosed with onychomycosis; 40 samples out of 192 (20.8%) were negative. Using M-PAS, filaments and/or spores were seen in 143 samples from the 152 positive (94%); 39 of them were negative to KOH/CB and positive to M-PAS (25.6%). With KOH/CB, filaments and/or spores were seen in 113 cases from the 152 positive samples (73.8% of the onychomycosis cases). Thirty-five cultures were positive, of which 77% were identified as Trichophyton rubrum; 117 onychomycosis cases were diagnosed despite the negative culture (76.9%). M-PAS showed 92.5% sensitivity and 55.55% specificity, a 67.5% positive predictive value and a 81.6% negative productive value.

Conclusions

This procedure, a combination of the existing methods to diagnose onychomycosis, KOH/CB together with a nail clipping biopsy, proved to have high sensitivity, as well as being rapid, easy, inexpensive and readily available in most hospital settings. M-PAS allowed us to diagnose 39 cases (25.6% of the cases of onychomycosis) that were false negative using only KOH/CB and culture.