Evaluation of Onychomycosis in Nail Psoriasis: Comparison of Diagnostic Methods
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Abstract
Background: Epidemiological studies indicate that onychomycosis may affect up to 79% of psoriatic patients. Onychomycosis in psoriatic patients is more commonly caused by yeasts comparing with non-psoriatic. There are different methods for diagnosing onychomycosis that could be used separated or together.
Objectives: To compare the histopathological findings (nail clipping) with Direct Mycological Examination (DME) and mycological culture on patients with psoriasis and nail psoriasis.
Methods: Eighty-three finger nails of 12 patients with the diagnosis of nail psoriasis were analyzed. None were under topical therapy or the nails. Samples for clipping, Direct Mycological Examination and mycological culture were collected. The proportions were analyzed using the chi-square test. The comparison of Direct Mycological Examination, mycological culture and clipping results were analyzed through sensitivity, specificity, positive and negative predictive value. Spss® 22 software was used for the analysis.
Results: Direct Mycological Examination x mycological culture: Direct Mycological Examination and mycological culture show agreement regarding their negative test. Of the 51 negative mycological culture exams, 5 were positive on Direct Mycological Examination and of the 51 negatives on Direct Mycological Examination, 5 were positive on mycological culture (p<0,0000). Therefore, Direct Mycological Examination and mycological culture are reliable and complementary methods on diagnosis of onychomycosis. Clipping x mycological culture: in the 51 negative mycological culture tests, were found 30 positive clipping tests (61.2%). Of the 34 negatives clipping, 13 were considered positive on mycological culture (38,2%) (p=0,96). Clipping x Direct Mycological Examination + mycological culture: Of the 56 negative results Direct Mycological Examination +mycological culture, 32 were positive on clipping (57,1%). Of the 34 negatives clipping, 10 were considered positive on Direct Mycological Examination + mycological culture (37%) (p: 0,613). This means that nail clipping “rescues” negative results from mycological culture. In Direct Mycological Examination there was a predominance of blastoconidia. No septae hyphae were detected. In mycological culture, the most prevalente fungi was Candida. There was no dermatophyte growth.
Conclusion: Nail clipping was positive more than half of the negative samples for mycological culture, and can be considered a great diagnostic aid, complementary to Direct Mycological Examination and mycological culture. These results are consistent with some previous reports, Candida was the fungus with higher frequency on the psoriatic nails, however, the role of these fungi is controversial (contamination x colonization x infection).
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