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Clinico-mycological correlation in onychomycosis in a tertiary level hospital.

Byline: Abu Noman Md Iftekhar Rafiq, A S M Zakaria, Lubna Khondker, Md Shirajul Islam Khan, Sharmin Doulah and Samaresh Chandra Hazra

Abstract Objective To correlate the clinical patterns of onychomycosis with the type of mycological agents in onychomycosis. Patients and methods In this cross-sectional study, 120 patients with onychomycosis, attending outpatient department, were selected by purposive type of sampling technique. They were subjected to thorough clinical examination. Nail material was collected for mycological diagnosis by microscopy and culture on dermatophyte test medium.

Results Microscopy was positive in 47 (39.2%) cases, whereas culture yielded Trichophyton rubrum in 53 (44.2%) and T. mentagrophytes in 2 (1.7%) patients. Common clinical nail changes in mycologically proven cases were thickening of nail plate (68.9%), subungual hyperkeratosis (63.9%), onycholysis (55.7%), roughening of nail plate (29.5%), yellowish discoloration (29.5%) and brownish-yellow discoloration (21.3%). Only, subungual hyperkeratosis was found significantly more in mycologically positive cases (63.9%) than in mycologically negative cases (37.3%), p Less than 0.05. The validity of microscopic examination for prediction of onychomycosis revealed sensitivity (74.5%), specificity (90.8%), accuracy (83.3%), positive predictive values (87.2%) and negative predictive values (80.8%).

Conclusion There is an insignificant correlation between clinical pattern and mycological diagnosis. No single clinical feature is suggestive of onychomycosis, hence, direct microscopy must always be coupled with fungal culture for accurate diagnosis.

Key words Clinical pattern, mycological pattern, onychomycosis.

Introduction

Onychomycosis denotes infection of the nail caused by dermatophyte fungi, nondermatophyte fungi or yeasts.1 It accounts for up to 50% of all nail disorders and 30% of all superficial fungal infections of skin.2,3 The dermatophytes cause the great majority of onychomycosis. Trichophyton rubrum is responsible for approximately 71% of all cases and T. mentagrophytes add another 20%. The nondermatophyte moulds Acremonium spp., Aspergillus spp., Fusarium spp., Onychocola canadensis, Scopulariopsis brevicaulis and Scytalidium dimidiatum account for approximately 4% of onychomycosis. Yeasts are the source of approximately 5% of onychomycosis, the majority of which is caused by Candida albicans.1

Onychomycosis expresses itself in various forms and clinically the disease is classified as distal and lateral subungual onychomycosis (DLSO), superficial white onychomycosis (SWO), proximal subungual onychomycosis (PSO), and candidal onychomycosis.4 Patient may have combination of these various forms.

Total dystrophic onychomycosis refers to most advanced form of any of the above.3,5 Nail changes in onychomycosis can occur in various forms, such as destruction of nail plate, roughening of nail plate, onycholysis, subungual hyperkeratosis, thickening and discoloration of nail plate (yellowish, brownish-yellow, whitish, blackish).6 Not necessarily all these nail changes should always be of fungal origin, they may occur in many other clinical mimickers e.g. psoriasis, lichen planus, eczema and contact dermatitis, chronic paronychia, hyperkeratotic (Norwegian) scabies, hemorrhage or trauma etc.7 So it is advisable to obtain a definitive diagnosis of fungal infection before initiation of antifungal therapy in case of dystrophic nails.

Mycological examination by direct microscopy (KOH preparation) combined with culture remains the gold standard technique for its reasonable cost and least inconvenience to the patient.5,7

Patients and methods

It was a cross-sectional study, conducted in the department of Dermatology and Venereology, BSMMU from January 2009 to December 2010. Hundred twenty patients with onychomycosis, attending in outpatient department, were selected by purposive type of non-probability sampling technique. Inclusion criteria were: clinically diagnosed cases of onychomycosis having onycholysis, subungual hyperkeratosis, discoloration, thickening of nail plate alone or in combination, patients of both sexes and all ages, patients who gave informed consent.

Exclusion criteria were patients who had received treatment either with topical and/or systemic antifungal agents for present nail condition within the last one month, diagnosed cases of other dermatological diseases having nail changes e.g. psoriasis, lichen planus, eczema, pityriasis rubra pilaris(PRP), Darier's disease.

Clinical assessment

Demographic data and specific data related to onychomycosis were noted. Clinically the disease was classified as follows: (i) distal and lateral onychomycosis (DLSO): If there was onycholysis, discoloration, subungual hyperkeratosis and thickening affecting the distal and/or lateral nail. (ii) superficial white onychomycosis (SWO): When chalky white spots were seen on or in the nail plate with textural changes. (iii) proximal superficial onychomycosis (PSO): If discoloration and onycholysis affected the proximal part of the nail. (iv) candidal onychomycosis (CO): When nail involvement was characterized by markedly thickened and roughened nail plates. The paronychial areas were red and edematous. (v) total dystrophic onychomycosis (TDO): If there was involvement of the entire nail bed and nail plate with thickening and roughening or destruction nail plate.

Specimen collection

The specimen was collected at laboratory of department of Microbiology and Immunology, BSMMU. The most severely affected nail was selected as the target nail where more than one nails were affected. When both finger- and toenails were involved simultaneously, specimens were collected from both sites after selecting target nails. The selected nail and surrounding skin were first cleaned with 70% alcohol to remove contaminants. In distal and lateral subungual onychomycosis the onycholytic nail plate was cut back as proximal as possible. Large piece of nail plate was cut into small by blade.

Microscopy

A part of the specimen was placed on a glass slide and 2-3 drops of 20% potassium hydroxide (KOH) was added. After thirty to sixty minutes slides were examined under microscope.

Culture

Dermatophyte test medium (DTM) was used for isolation of dermatophytes. The test tubes were incubated at room temperature and checked out regularly for 1-2 weeks before declared as negative, as dermatophyte tends to grow slowly. When a dermatophyte grows in DTM medium, its orange color changes to red. Phenol red, a pH indicator is one of the constituents of DTM. When phenol red is affected by the alkaline metabolites of dermatophytes, it imparts red color to the medium. The pathogenic organisms were identified by gross colony morphology and microscopic examination of lactophenol cotton blue (LCB) preparations.

Data were analyzed and checked for inadequacy, irrelevancy, and inconsistency by using SPSS (statistical package of social science) software 16.

Results

Out of 120 patients, direct microscopy was positive in 47 (39.2%) cases. On culture, 55 (45.8%) samples showed a dermophyte growth; 53 (44.2%) specimens grew Trichophyton rubrum and 2 (1.7%) T. mentagrophytes (Table 1).

On microscopic examination for evaluation of onychomycosis, there were 41 true positive, 6 false positive 6, 14 false negative and 59 true negative cases. The result is shown Table 2.

Correlation between the clinical nail changes and their diagnostic value (Table 3) showed that thickening of nail plate, onycholysis, subungual hyperkeratosis, roughening of nail plate, yellowish discoloration and brownish-yellow discoloration were the frequent changes. However, except the subungual hyperkeratosis, none clinical feature significant correlated with mycological diagnosis. Subungual hyperkeratosis was found 39 (63.9%) and 22 (37.3%) culture positive and negative, respectively (p Less than 0.05).

Regarding the causative pathogen and the clinical type of onychomycosis (Table 4), T. rubrum was isolated from all types of onychomycosis i.e. DLSO (50.9%), TDO (45.3%) and in SWO (14.3%). T. mentagrophytes was isolated only in 2 cases of DLSO (3.8%). No significant (p greater than 0.05) correlation existed between the clinical pattern of onychomycosis and causative species of fungus (Table 4).

Table 1 Microscopic and culture examination of the study patients (n=120)

###N (%)

Microscopic examination

Positive###47 (39.2)

Negative###73 (60.8)

Culture report

Trichophyton rubrum###53 (44.2)

T. mentagrophytes###2 (1.7)

E. floccosum###0 (0)

No growth###65 (54.2)

Table 2 Comparison between microscopic examination and culture for prediction of onychomycosis (n=120).

KOH smear###Culture###Total

###Positive###Negative

Positive###41###6###47

Negative###14###59###73

Total###55###65###120

Table 3 Association between pattern of nail changes and their diagnostic (Microscopy and Culture) value.

###Positive###Negative###Sensitivity Specificity###p value

Pattern of nail changes###(n=61)###(n=59)

Thickening of nail plate###Present###42 (68.9%)###46 (78%)###68.9###22.0

###0.259ns

Thickening of nail plate###Absent###19 (31.1%)###13 (22%)

Subungual hyperkeratosis Present###39 (63.9%)###22 (37.3%)###63.9###62.7

###0.004s

Subungual hyperkeratosis###Absent###22 (36.1%)###37 (62.7%)

Onycholysis###Present###34 (55.7%)###33 (55.9%)###55.7###44.1

###0.982ns

Onycholysis###Absent###27 (44.3%)###26 (44.1%)

Roughening of nail plate-###Present###18 (29.5%)###24 (40.7%)###9.8###69.0

###0.199ns

Roughening of nail plate-###Absent###43 (70.5%)###35 (59.3%)

Destruction of nail plate- Present###6 (9.8%)###1 (1.7%)###10.9###98.5

###0.062ns

Destruction of nail plate- Absent###55 (90.2%)###58 (98.3%)

Yellowish discoloration###Present###18 (29.5%)###20 (33.9%)###29.5###66.1

###0.607ns

Yellowish discoloration###Absent###43 (70.5%)###39 (66.1%)

Brownish-yellow discolor Present###13 (21.3%)###16 (27.1%)###21.3###72.9

###0.457ns

Brownish-yellow discolor###Absent###48 (78.7%)###43 (72.9%)

Whitish discoloration###Present###4 (6.6%)###5 (8.5%)###6.6###91.5

###0.478ns

Whitish discoloration###Absent###57 (93.4%)###54 (91.5%)

Blackish discoloration###Present###5 (8.2%)###5 (8.5%)###8.2###91.5

###0.607ns

Blackish discoloration###Absent###56 (91.8%)###54 (91.5%)

Chalky white spot###Present###2 (3.3%)###2 (3.4%)###3.3###96.6

###0.677ns

Chalky white spot###Absent###59 (96.7%)###57 (96.6%)

Pitting###Present###0 (0)###2 (3.4%)###0###96.9###0.239ns

Pitting###Absent###61 (100%)###57 (96.6%)

p value reached from Chi square test, NS= not significant, S= Significant

Table 4 Association between clinical patterns with mycological agents (n=120)

Clinical patterns###T. rubrum###T. mentagrophytes###Sensitivity Specificity Value

###(n=53)###(n=2)

###N###%###n###%

DLSO (n=53)

###Present###27###50.9###2###3.8

###51.1###0.0###0.180ns

###Absent###26###49.1###53###96.2

SWO (n=14)

###Present###2###3.7###0###0.0

###3.7###100.0###0.781ns

###Absent###12###96.3###14###100.0

TDO (n=53)

###Present###24###45.3###0###0.0

###44.4###100.0###0.212ns

###Absent###29###54.7###53###100.0

NS= Not significant (p greater than 0.5), p value reached from Chi square test. DLSO=distal and lateral subungual onychomycosis, SWO= superficial white onychomycosis, PSO=proximal subungual onychomycosis.

The validity of microscopic examination for prediction of onychomycosis was calculated as sensitivity (74.5%), specificity (90.8%), accuracy (83.3%), positive predictive values (87.2%) and negative predictive values (80.8%).

Discussion

Direct microscopy of KOH mount is important to confirm the clinical diagnosis while culture of the fungus is required to identify the pathogenic organism causing onychomycosis.

The result of both may vary as direct microscopy relatively easy while culture needs technical expertise. For instance Gupta et al.3 showed that among 130 patients, DLSO was the most common clinical type, seen in 93(73.1%) of the patients, followed by candidal onychomycosis in 19 (46.1%), TDO and WSO with 9 (7.7%) and 6 (4.6%) patients. KOH and culture positivity were recorded in 59.2% and 37.6% cases, respectively.

Both KOH and culture positivity were seen in 40 (30.8%) samples. Dermatophytes and yeast (Candida albicans) were isolated in 40.8% each of the cultured nail specimens, while nondermatophyte moulds were cultured in 18.4% of the samples. Various dermatophytes cultured were T. rubrum (32.6%), T. mentagrophytes (6.1%) and T. verrucosum (2.1%), respectively. Aspergillus spp. (6.1%) was the most commonly isolated NDM, while other detected moulds were Acremonium spp., Fusarium spp., Scopulariopsis spp. and 3 Penicillium marneffei.

In our study microscopy and culture positivity were 39.2% and 45.8%, respectively. Dermatophytes, the most common cause of onychomycosis in other reports, were also the most frequent pathogen found in this study. Of the dermatophytes, T. rubrum (44.2%) was the most common organism as reported for other countries such as Finland, Spain, UK and USA.

In a study of 90 patients with onychomycosis, Grag et al.6 found dermatophytes as the most common pathogens, isolated in 24 (26.36%) patients [T. rubrum (23.07%), T. verrucosum (2.22%), and E. floccosum (1.11%)], followed by C. albicans in 22 (24.27%) and nondermatophyte moulds in 36 (39.58%). The 36 non-dermatophyte moulds were isolated from 29 cases. Of these 29 cases, six were associated with T. rubrum, which was considered the primary pathogen. T. rubrum and C. albicans were the major pathogens. The clinico- mycological correlation revealed that a single pathogen could give rise to more than one clinical type.

T. rubrum appeared as the most common dermatophyte in our study, as well, causing DLSO (51.9%), TDO (45.3%) and SWO (14.3%). T. mentagrophytes was detected in 2 (3.8%) cases of the DLSO only. Statistically no significant correlation was found between the clinical type of onychomycosis with the mycological agents. This is similar to the results of Das et al.

Out of their 85 cases, 44 showed the presence of fungus (either by KOH preparation and/or fungal culture) amounting to 51.76% positivity. Among those 44 cases, the infecting fungal agents were dermatophytes in 22 (50%) cases, yeasts in 12 (27.27%) and moulds in 10 (22.72%). T. rubrum accounted for the majority of dermatophytes in 13 (29.54%), C. albicans was the predominant yeast in 10 (11.78%) and A. niger was the commonest mould in 8 (18.18%) cases.

No significant correlation between clinical features and mycological diagnosis was noted except for melanonychia (p=0.0151) and subungual hyperkeratosis (p=0.0299), which were found to be more significantly associated with non- onychomycotic etiology of nail changes. No significant association could be established between the different fungal species and various clinical presentations when the factors were subjected to univariate analysis. Direct microscopy was positive in 28 (63.64%) cases and fungal culture in 42 (92.45%) cases out of 44 cases diagnosed with onychomycosis. False negative result was found in 16(36.36%) cases with direct microscopy and 2 (4.54%) cases with fungal culture.

The present study reaffirms that diagnosis of onychomycosis based on the clinical nail changes is often misleading since only 61 (50.8%) of the cases clinically diagnosed as onychomycosis showed the presence of fungus. Other workers from different geographical locations reported similar results of mycological confirmation of clinically prediagnosed onychomycosis in only 43.7% in Poland, 50.6% 7 in Turkey and 45.53% in India by Das et al.

In one study by Sayed et al.8 among 772 patients, direct microscopy was positive in 256 cases (33.2%). Of this, 230 showed positive cultures and 26 negative culture. However, fungal cultures were positive in 419 patients (54.3%; 260 women and 159 men). The most common pathogens isolated were dermatophytes (60.1%), Candida albicans (14%), nondermatophyte moulds (3.5%). Among dermatophytes, the most commonly isolates were T. mentagrophytes (36%), T. rubrum (27.5%) and T. tonsurans 8 (26%).

In an observational study by Bokhari et al.9 the various clinical types noted were DLSO (47%), CO (36%), TDO (12%), SWO (3%) and PSO (2%). Candida was the most common pathogen (46%) followed by dermatophyte (43%) [T. rubrum (31%), T. violaceum (5%), T. mentagrophytes (4%), T. tonsurans (2%) and E. floccosum (1%)] and nondermatophyte moulds (11%). Onychomycosis was more common in 9 women of 20-40 years of age.

In one study by Kaur et al.10 T. rubrum was the commonest fungus isolated (46.67%). T. mentagrophytes, C. albicans accounted for 20% and 15.56% isolates, respectively. Samples from only 41 patients were subjected to periodic acid- Schiff (PAS) staining and 21 (51.22%) were reported PAS sensitive. T. rubrum was the commonest isolates obtained from case of DLSO and TDO and only isolates obtained from PSO was T. rubrum. T. mentagrophytes was isolated from two cases of SWO and A. niger from third cases.10 This is also in accordance with our study.

Adhikari et al.11 in 2009 studied 34 clinically suspected cases of onychomycosis, out of which 32 (94.12%) were positive for fungal elements by direct microscopy and 28 (82.35%) by culture. Of 28 isolated fungi, 18 (64.29%) were identified as dermatophytes. T. tonsurans (44.44%) was the common isolate, followed by T. mentagrophytes (22.22%), T. rubrum (11.11%), T. verucosum (11.11%) and Microsporum audouinii (11.11%). Apart from dermatophytes, A. niger (21.43%) and P. marneffei (14.28%) were also isolated.11

A study was undertaken in 488 patients suspected of onychomycosis by Chadeganipour et al.12 in 2008, onychomycosis was found to be the commonest in housewives, followed by laborers working in petroleum industry and office workers. Direct microcopy of the nail clips was positive in 194 (39.8%).

As agent of onychomycosis, yeasts were detected in 112 (57.7%), dermatophytes in 27 (13.9%) and nondermatophyte fungi in 55 (28.4%) patients. Of the samples cultured, C. albicans was the most prevalent (84%) yeast. Among dermatophyte, T. mentagrophytes was found to be the commonest etiological agent (8.6%) followed by E. floccosum (2.7%) and T. rubrum (2.2%). It was mentioned that nondermatophyte moulds were isolated from the same nails, during the repeated direct microscopy and cultures to confirm them as etiological agents of onychomycosis. Moreover, 9 samples with positive direct microscopy yielded no growth.

Conclusion

Although onychomycosis is a frequent cause of nail dystrophy, it is not always possible to make an accurate diagnosis based on clinical grounds alone. The pattern of nail changes cannot be taken as a reliable marker for predicting the causative organism. To evaluate the pattern with onychomycosis direct microscopy must always be coupled with fungal culture for accurate diagnosis.

References

1. Verma S, Hefferman MP. Fungal diseases: onychomycosis. In: Wolff K, Goldsmith LA, Katz S et al., editors. Fitzpatrick's Dermatology in General Medicine. 7th edn. New York: McGraw-Hall Companies; 2008. pp. 1817-8.

2. James WD, Berger TG, Elston DM, editors.

Andrews' Diseases of Skin Clinical Dermatology. 10th edn. Philadelphia, USA: Elsevier; 2006. P. 305-6. 3. Gupta M, Sharma NL, Kanga AK et al. Onychomycosis: Clinicomycologic study of 130 patients from Himachal Pradesh, India. Indian J Dermatol Venereol Leprol. 2007;73:389-92.

4. Hay RJ, Moore MK. Mycology: Superficial and cutaneous mycoses. In: Burns T, Breathnach S, Cox N, Griffiths C, editors. Rook's Textbook of Dermatology. 7th edn, Massachusetts, USA: Blackwell; 2004, p.31.37.

5. Tosti A. Onychomycosis. Updated: May 5, 2010. Retrieved June 20 2010 from http://emedicine.medscape.com/article/1105 828-overview.

6. Grag A, Venkatesh V, Singh M et al. Onychomycosis in central India: A clinico- etiologic correlation. Int J Dermatol. 2004;43:498-502.

7. Das NK, Ghosh P, Das S et al. A Study on the etiological agent and clinico- mycological correlation of finger nail onychomycosis in Eastern India. Indian J Dermatol. 2008;53:75-9.

8. Sayed FE, Ammoury A, Haybe RF, Dhaybi R. Onychomycosis in Lebanon: A mycological survey of 772 patients. Mycosis. 2006;49:216-9.

9. Bokhari MA, Hussain I, Jahangir M et al. Onychomycosis in Lahore, Pakistan. Int J Dermatol. 1999;38:591-5.

10. Kaur R, Kashyap B, Makkar R. Evaluation of clinico-mycological aspects of onychomycosis. Indian J Dermatol. 2008;53:174-8.

11. Adhikari L, Gupta AD, Pal R, Singh TSK. Clinico-etiologic correlates of onychomycosis in Sikkim. Indian J Pathol Microbiol. 2009;52:194-7.

12. Chadeganipour M, Nilipour S, Ahmadi G. Study of onychomycosis in Ispahan, Iran. Mycosis. 2008;52:153-7.

Infectious Diseases Hospital, Dhaka Department of Dermatology and Venereology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka Combined Military Hospital, Dhaka Cantonment, Dhaka WHO-Dhaka City Corporation, Dhaka
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Author:Rafiq, Abu Noman Md Iftekhar; Zakaria, A S M; Khondker, Lubna; Khan, Md Shirajul Islam; Doulah, Shar
Publication:Journal of Pakistan Association of Dermatologists
Article Type:Report
Geographic Code:9PAKI
Date:Sep 30, 2013
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