FC‐47 Comparison of four different types of stain in ear cytology

Swab cytology is one of the most useful and rapid methods to assess the presence of external infections in ear canals. Smears are generally stained with Romanowsky‐type stains, with or without prior heat fixation. The aim of this study was to compare four different ways of staining ear cytology swab samples. Eight animals with ceruminous or purulent otitis externa were selected. Cotton swabs were introduced in a total of 12 ear canals, and four cytologic samples on four different slides were obtained from each swab. Glass slides were air‐dried and randomly identified with the number of the ear canal and the letters A, B, C or D. Slides marked with A were heat‐fixed and stained with Dip Quick ® ; slides marked with B were stained without heat fixation. Slides marked with C were heat‐fixed and dipped in the blue colour only; slides marked with D were stained in the blue colour only without prior heat fixation. Ten high‐power fields (oil immersion) were evaluated for each slide, and keratinocytes, yeasts, bacteria and neutrophils were counted. A statistical comparison was performed with parametric (Student's t ‐test applied after verifying the normal distribution of the data) and nonparametric tests (Wilcoxson's and signs’ tests). There were no significant differences between the four staining methods ( P  ≤ 0.05). The authors conclude that heat fixation does not improve the cytological evaluation of ear swab samples and propose a one‐step dip in the blue colour only as a rapid method of staining cytological samples from ear canals. Funding: Self‐funded.