|Year : 2018 | Volume
| Issue : 1 | Page : 39-41
A simple but yet novel stain in the diagnosis of onychomycosis
Thansiha Nargis, Manjunath Mala Shenoy, Vishal Bejai, Vaishnavi Gopal
Department of Dermatology, Venereology and Leprosy, Yenepoya Medical College, Yenepoya University, Mangalore, Karnataka, India
|Date of Web Publication||22-May-2018|
Dr. Thansiha Nargis
Department of Dermatology, Yenepoya Medical College, Yenepoya University, Deralakatte, Mangalore - 575 018, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Onychomycosis can resemble other nail dystrophies and hence the clinical diagnosis should be supplemented with a laboratory diagnosis. Rapid diagnosis of onychomycosis is the necessary to initiate early therapy. In this study, the efficacy of Chicago Sky Blue (CSB) stain in comparison with that of routine potassium hydroxide (KOH) preparation in the diagnosis of onychomycosis was evaluated. Methods: A prospective study of 42 nails with a clinical diagnosis of distal lateral subungual onychomycosis. KOH mount followed by direct microscopic examination of the subungual debris was performed. This was followed by microscopic examination after addition of 1% CSB. Results were interpreted by two experienced dermatologists. Results: 18 (42.9%) nails showed KOH positivity and 37 (88.1%) were positive for CSB stain. Conclusions: CSB staining was more sensitive and was more accurate in the rapid diagnosis of onychomycosis. Colour contrast provided by the CSB made it easier identification of fungal elements.
Keywords: Chicago sky blue stain, onychomycosis, potassium hydroxide mount
|How to cite this article:|
Nargis T, Shenoy MM, Bejai V, Gopal V. A simple but yet novel stain in the diagnosis of onychomycosis. Indian J Dermatopathol Diagn Dermatol 2018;5:39-41
|How to cite this URL:|
Nargis T, Shenoy MM, Bejai V, Gopal V. A simple but yet novel stain in the diagnosis of onychomycosis. Indian J Dermatopathol Diagn Dermatol [serial online] 2018 [cited 2020 Feb 25];5:39-41. Available from: http://www.ijdpdd.com/text.asp?2018/5/1/39/232950
| Introduction|| |
Onychomycosis has to be differentiated from other causes of nail dystrophy before treating them with antifungals. Detecting fungal elements in the nail is time-consuming and often difficult to visualize using conventional methods such as potassium hydroxide (KOH) mount. Many stains such as the Parker blue–black ink, Swartz-Lamkins stain, Chlorazole-KOH, KOH-acridine orange stain, and Calcofluor White with KOH stains both the dermatophytes and the Malassezia species have been described.,,, The Chicago Sky Blue (CSB) 6B (Direct Blue 1) stain along with KOH was helpful in the rapid detection and also improving the accuracy of nail fungal elements in routine dermatophytosis. Very few studies have been conducted to explore the utility of CSB staining in the diagnosis of onychomycosis.
| Materials and Methods|| |
A total of 42 nails from 36 patients with a clinical diagnosis of distal lateral subungual onychomycosis (DLSO) were selected for the study. Subungual debris was collected from the under the surface of the infected nails as proximal as possible after cleaning with 70% alcohol. A drop of 20% KOH was added and the slides were left at room temperature for 30 min. Examination of the mount was done under microscope for the fungal elements by two experienced dermatologists. Slides showing branching hyphae were considered as positive. A drop of 1% CSB stain was added to the mount and examined under microscope after 10 min by the same dermatologists. CSB stain was prepared by dissolving 1 g of the CSB dye in 100 ml of distilled water forming approximately 1% solution., Positive results were considered when blue filaments were noted.
| Results|| |
Out of the 42 nails with clinical distal lateral onychomycosis, we detected fungal elements from 18 nails (42.9%) [Table 1] using KOH preparation [Figure 1]. All these positive slides were also positive with CSB staining. An addition of nails which were negative by KOH preparation [Figure 2] were detected to be positive by CSB staining making a total 37 positive results (88.1%) [Figure 3] and [Figure 4]. Among the 42 nails, fungal elements could not be detected in 5 nails both by KOH preparation and CSB staining. Although we did not notice the color contrast mentioned by the other articles, we noted that the fungal hyphae stained deeply to give a bluish color when left for a longer time. Fungal elements which were not visualized on KOH preparation due to incompletely lysed keratin [Figure 2] was visualized when CSB staining was performed [Figure 3].
|Figure 1: Microscopic examination of potassium hydroxide preparation of subungual debris of onychomycosis showing fungal hyphae (×10)|
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|Figure 2: Microscopic examination of potassium hydroxide preparation of subungual debris that was negative for fungal elements (×10)|
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|Figure 3: Branching fungal filaments identified in the slide that was negative for potassium hydroxide preparation after adding 1% Chicago Sky Blue (×10)|
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|Figure 4: Chicago Sky Blue stain (×40): Morphology of the fungal elements clearly visible with branching filaments and septations|
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| Discussion|| |
Diagnosing onychomycosis is a challenge as well as time-consuming. Mycological confirmation requires weeks to isolate the agent on culture and often the yields on culture are poor., The initiation of antifungal therapy is often based on the interpretation of direct examination such as KOH preparation. The interpretation of KOH mount often requires skills, and at times, it has been reported as false negative even by experienced persons., The detection of fungal elements by KOH mount from a nail clipping takes a longer time for it to be lysed. In this study, CSB staining could confirm significantly more cases of onychomycosis compared to KOH preparation (88.1% v/s 42.9%). Time taken for the CSB staining is a 10 min addition to the KOH preparation totaling to about 40 min; hence, it is a rapid test for the diagnosis. The percentage of cases with KOH positivity would have increased if the nails were left longer for a period of 2 h or more. Utilizing CSB staining abolishes this waiting period and also enhances the ease of identifying the fungus. We need a rapid method for the diagnosis as well as a simple staining technique since most laboratories in our country are equipped only with basic infrastructure and limited qualified workforce. We found a number of staining procedures which were helpful for the rapid detection of fungal elements, but each had its own drawbacks.,, Panasiti et al. compared chlorazol-KOH and KOH-acridine orange in diagnosing onychomycosis and noticed to have a sensitivity of 55% and 39%, and specificity of 74% and 85%, respectively, but it needed a fluorescent microscope. Calcofluor-white has shown to be 87% sensitive and 89% specific for the diagnosis of onychomycosis, and it also requires a fluorescent microscope for the analysis. Swartz-Lamkins stain was difficult to prepare and was not effective in thicker specimens like nail. Periodic acid–Schiff stain has 90% sensitivity in identifying fungal elements, but the staining is used in the histopathological sections.
CSB is a dye used in the textile industry, inks, and paints and also as a counterstain in immunohistochemistry. Studies by Lim and Lim et al. showed that the CSB is more sensitive and more specific than the KOH preparation. CSB provides a color contrast that makes the easier location of fungal elements even when they were scanty. It also highlighted the morphologic characteristics of both spores and hyphae and enabled oil-immersion examination., In this study, we observed that though the nail scrapings did not lyse, the fungal hyphae and spores had taken up the stain making the identification of the fungal elements. The staining could be observed in a simple microscope, could be easily performed in a basic office setting and by a person not highly trained in the laboratory. The stain occasionally has been seen to have taken up by artefacts, but a careful observation can distinguish them from the fungus. The limitations of this were small study group and comparison with fungal culture or nail histopathology as a gold standard method would have increased the accuracy of the results.
| Conclusion|| |
CSB stain is an inexpensive, rapid office procedure that requires less skill than the routine.
KOH preparation. It can be used as a routine test in the diagnosis of superficial fungal infections, especially onychomycosis.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]