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

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 x400 and x1000 magnification. Results The number of yeasts per unit surface area was significantly higher at x1000 compared to x400 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 x1000 magnification. The repeatability of this examination for counting the yeasts is poor.