Repeatability and reproducibility of microscopic examination of adhesive tape strip cytology slides for the quantification of Malassezia spp. in canine skin.

Abstract

BACKGROUND: The optimal microscopic magnification and number of optical fields of adhesive tape strip cytological slides that should be examined when searching for Malassezia yeasts on canine skin are unknown. OBJECTIVES: To determine the optimal magnification and the minimum number of optical fields that should be examined to maximise intraobserver repeatability and interobserver reproducibility. MATERIALS AND METHODS: Seven experienced examiners counted, twice, the number of yeasts in 10, 20, 30, 40 and 50 optical fields of 40 slides at ×400 and ×1000 magnification. RESULTS: The number of yeasts per unit surface area was significantly higher at ×1000 compared to ×400 magnification. Repeatability and reproducibility for counting the yeasts was very poor. CONCLUSIONS AND CLINICAL RELEVANCE: Adhesive tape strip cytological slides should be examined microscopically for Malassezia spp. at ×1000 magnification. The repeatability of this examination for counting the yeasts is poor.