|Year : 2021 | Volume
| Issue : 2 | Page : 57-60
Evaluation of fungal elements in dystrophic nails using Chicago sky blue stain
TN Revathi, Sowmya S Aithal
Department of Dermatology, Venereology and Leprology, Victoria Hospital, Bengaluru, Karnataka, India
|Date of Submission||01-Feb-2021|
|Date of Decision||27-Jun-2021|
|Date of Acceptance||05-Jul-2021|
|Date of Web Publication||06-Oct-2022|
Sowmya S Aithal
4753/A, Sindhoora, Opposite Jyothi IVF Centre, Dattagalli 3rd Stage, Mysore 570022, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Dystrophic nails represent an alteration in nail morphology that can occur due to various disorders. Although KOH is used commonly in the diagnosis, the sensitivity and specificity of KOH are less. Chicago sky blue (CSB) stain when used with KOH provides color contrast, to aid the detection of fungal elements, and is a simple and inexpensive method. Materials and Methods: Nail scrapings from the surface and subungual areas and nail clippings were examined with 40% KOH, CSB stain, and also subjected to fungal culture. Results: The detection rate of fungal elements in dystrophic nails in our hospital-based study was 46.5%. The sensitivity of KOH was 36.36% and CSB staining was 66.6% using fungal culture as a gold standard. Conclusion: CSB stain serves as a useful, simple, and rapid method for detecting the presence of fungal elements.
Keywords: Chicago sky blue stain, dystrophic nails, onychomycosis
|How to cite this article:|
Revathi T N, Aithal SS. Evaluation of fungal elements in dystrophic nails using Chicago sky blue stain. Indian J Dermatopathol Diagn Dermatol 2021;8:57-60
|How to cite this URL:|
Revathi T N, Aithal SS. Evaluation of fungal elements in dystrophic nails using Chicago sky blue stain. Indian J Dermatopathol Diagn Dermatol [serial online] 2021 [cited 2023 Feb 8];8:57-60. Available from: https://www.ijdpdd.com/text.asp?2021/8/2/57/357932
| Introduction|| |
Onychodystrophy represents various pathologic processes of the nails including infectious and non-infectious diseases such as onychomycosis, psoriasis, and irritant and allergic dermatitis. The most frequent nail disorders are onychomycosis (30–40%) and nail psoriasis.
Potassium hydroxide (KOH) preparation and fungal culture, which are typically utilized in the diagnosis of fungal infections, often yield false-negative results. Chicago sky blue (CSB) is a new stain, which contains 1% CSB 6B and is used with KOH. It provides color contrast that helps in the easier detection of fungal elements even when they are scanty.
Aims and objectives
The aim of this article is to detect the presence of fungal elements in scrapings from the surface and subungual areas of dystrophic nails with CSB stain and to compare the efficacy of CSB stain-KOH with KOH and fungal culture.
| Materials and Methods|| |
Institutional Ethical Committee clearance was obtained for this cross-sectional study conducted on 71 patients presenting with dystrophic nails. Patients of age 18–60 years and of either sex presenting with dystrophic nails, defined as an alteration in nail morphology manifesting as misshapen and damaged nails, were included. Patients who were already on antifungal treatment for onychomycosis were excluded.
After history taking and clinical examination, nail scrapings from the surface and subungual areas and nail clippings were taken and divided into three parts. One part was examined after adding a drop of 40% KOH after 30 min. The second part was treated with KOH–1% CSB combination and examined under the microscope at 10× and 40× magnifications after 10 min. CSB stain was prepared by dissolving 1 g of CSB dye in 100 mL of distilled water forming a 1% solution. The third part of the sample was subjected to fungal culture.
| Results|| |
In our study, 54% were males, and the remaining 46% were females. The highest prevalence (47.8%) was seen in participants of the age group 40–60 years and the lowest prevalence (4.22%) in participants younger than 20 years. Of 71 cases, 22.5% of the participants were housewives, 12.7% were farmers, 12.7% were students, 9.85% were laborers, and the remaining 42.25% performed other occupations.
The most common clinical type in our study was distal and lateral subungual onychomycosis (DLSO) in 63.6% of the cases, followed by proximal subungual onychomycosis [Figure 1]. Dermatophytes were the most commonly found pathogens (57.57%), followed by non-dermatophyte molds isolated in about 24.24% of the participants. Among the dermatophytes, Trichophyton rubrum was the most frequently isolated in about 33.33% of the participants [Table 1].
|Figure 1: Frequency distribution of patients according to clinical type of onychomycosis|
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|Table 1: Frequency distribution of fungal isolates observed by clinical pattern|
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Among the 71 patients who presented with dystrophic nails, fungal elements could be detected in 33 (46.48%) patients by fungal culture. KOH preparation alone could detect fungal elements only in 12 (16.9%) cases, whereas CSB stain could detect in 22 (30.9%) cases [Figure 2] and [Figure 3]. False-negative results were found in 22 cases with KOH and in 11 cases with CSB staining, i.e., 10 nails that were shown negative by KOH could be detected by CSB stain with the aid of color contrast [Figure 4]. Comparison of results of direct microscopy with KOH, CSB stain, and fungal culture in the diagnosis of onychomycosis is depicted in [Table 2] and [Table 3].
|Figure 2: CSB stain of nail sample showing fungal elements with color contrast (10×)|
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|Figure 3: Bluish septate hyphae seen with faint pink background in CSB stain under 40×|
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|Figure 4: Fungal filaments identified in the slide with 1% CSB that was negative for potassium hydroxide preparation|
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|Table 2: Comparison of results of direct microscopy with KOH and fungal culture in the diagnosis of onychomycosis|
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|Table 3: Comparison of results of direct microscopy with CSB stain and fungal culture in the diagnosis of onychomycosis|
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With fungal culture as the gold standard, the sensitivity of KOH was 36.36% and CSB stain was 66.6% and their specificity came out to be 100% (P < 0.01), suggesting CSB sensitivity to be superior to KOH.
| Discussion|| |
The detection rate of fungal elements in dystrophic nails in our hospital-based study was 46.5%. Few studies have shown isolation rates of 39.5% in Central Delhi, India and 37.6% in Himachal Pradesh, India. Many patients with dystrophic nails may not seek medical attention, which explains the difference in the prevalence observed.
Higher prevalence in elderly patients can be due to the presence of repeated trauma, poor immunity, other comorbidities, and increased duration of exposure to causative fungi.
Males are more predisposed than females because of nail damage from increased outdoor exposure, more physical activity, and frequent use of occlusive footwear.
Housewives are more involved in household work like washing clothes, vegetables, and cleaning house, which makes them prone to trauma and exposure to moisture. Farmers and laborers have frequent physical trauma due to their nature of work making them prone to dystrophy.
In our study, patients presented to us with different cutaneous features. The most common association was psoriasis in 14% of cases. Other associations included eczema (8.45%), Tinea corporis (7.04%), lichen planus (4.22%), pemphigus vulgaris (4.22%), Tinea cruris (2.81%), bullous pemphigoid (2.81%), and atopic dermatitis (1.4%). Dystrophic nails in psoriatic patients lose their natural preventing barrier and thus are more predisposed to fungal infection. Nail psoriasis acts as a risk factor specifically for dermatophytic nail infections.
Of the 71 patients with dystrophic nails, 43.48% were shown to have fungal elements by culture, 30.9% by CSB stain, and only 16.9% by KOH in our study. The sensitivity of CSB stain was higher than that of KOH.
KOH examination alone will lead to significant under-diagnosis of cases, whereas fungal culture increases the gap between diagnosis and cure because it requires weeks for growth and the yield is also poor.
Staining with CSB requires 10 min in addition to KOH preparation that requires 40 min. Hence, it is a rapid and inexpensive method using a simple microscope. It provides good color contrast in comparison to KOH, helping in the rapid detection of fungal elements. It also highlights the morphology of fungi helping in the detection of yeast and hyphae.
Studies have shown that the CSB is more sensitive and more specific than the KOH preparation. The cost for a 25 g bottle of CSB, which stains about 1500 specimens, is only 3500₹ and thus economical.
Many studies have shown several staining procedures like Calcofluor-White Stain and KOH-Acridine Orange Stain, helpful for the rapid detection of fungal elements but they are expensive and require a fluorescent microscope.,
Histopathological examination of nail clippings with PAS stain renders diagnosis in a short time and more sensitive than KOH and culture. But it is an invasive method, does not identify the particular pathogen and serum inclusions may be mistaken for fungi which are also PAS-positive.
Fungal culture is considered as a gold standard for mycological examination but it requires weeks for results and the yields are poor.
The presence of fungal elements in dystrophic nails can act as a reservoir of fungus which may spread to other areas. It is important to establish a diagnosis before starting patients on a long course of antifungal treatment. The limitations of this study include a small study group.
| Conclusion|| |
In conclusion, the present study shows 46.5% of dystrophic nails to be of fungal etiology and CSB stain could detect 30.9% of cases. Dystrophic nails caused by different conditions pose a diagnostic challenge and mycological examination is required to start patients on a long course of antifungal treatment in addition to clinical examination. Hence, CSB stain serves as a useful, simple, and rapid method for detecting the presence of fungal elements, which is less skill dependent than the routine KOH preparation and requires only an ordinary light microscope, compared with other stains which require a fluorescent microscope for examination.
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]
[Table 1], [Table 2], [Table 3]