Evaluation of the value of staining hair samples with a modified Wright-Giemsa stain and/or showing illustrated guidelines for the microscopic diagnosis of dermatophytosis in cats

Rareş Căpitan; Carlo Schievano; Chiara Noli

doi:10.1111/vde.12543

Evaluation of the value of staining hair samples with a modified Wright-Giemsa stain and/or showing illustrated guidelines for the microscopic diagnosis of dermatophytosis in cats

Vet Dermatol. 2018 Apr 17. doi: 10.1111/vde.12543. Online ahead of print.

Authors

Rareş Căpitan¹, Carlo Schievano², Chiara Noli³

Affiliations

¹ Regatul Animalelor, Sos. Panduri 31, bl P2, sector 5, RO-050655, Bucharest, Romania.
² Department of Compared Biomedicine and Food Science, University of Padova, Viale dell'Università 16, 35020, Legnaro, PD, Italy.
³ Servizi Dermatologici Veterinari, Strada Bedale della Ressia 2, 12016, Peveragno, CN, Italy.

PMID: 29664175
DOI: 10.1111/vde.12543

Abstract

Background: Direct examination of the hair is a simple diagnostic test for the diagnosis of dermatophytosis; training is needed to use this test.

Hypothesis/objectives: To evaluate whether use of modified Wright-Giemsa blue stain and/or photographic images of infected and uninfected hairs improved the user's ability to identify infected or uninfected hairs.

Animals: Ten cats with, and 10 cats without, dermatophytosis due to Microsporum canis (n = 20).

Materials and methods: Twenty unstained and 20 stained hair samples from each group (n = 40) were anonymized and examined by veterinarians using a light microscope. Participants recorded samples as "infected" or "uninfected". Participants were then shown and allowed to use photographic images while examining the same 40 samples.

Results: Without staining, investigators correctly identified 12.7 ± 4 of the 20 samples (mean ± SD) and with staining 13.6 (±3). After illustrative guidelines were shown, they correctly identified a mean of 16.9 (±2.5) unstained slides and 15.8 (±2.3) stained slides. "Illustrated guidelines" and "hair infection" significantly increased the probability of a correct answer, whereas "staining" did not. Logistic regression determined that "study participant", "illustrated guidelines" (OR = 2.6) and "hair infection" (OR = 2.1) had a significant influence on the results, whereas "staining" did not. Sensitivity and specificity of direct examination were 70.5% and 56%, respectively, compared with culture status.

Conclusions and clinical importance: When examining hairs for the presence or absence of infected dermatophyte hairs, diagnostic accuracy was improved when observers used illustrated guides compared with just examining stained slides.