In-house testing in Small Animal Dermatology

There are basic tests in which every practice interested in dermatology should become proficient and which can be performed and evaluated quickly in house, these are covered in this lecture.

Cytology

A. General Comments We sample any chronic and pruritic skin condition and all cases with otitis externa. Secondary microbial infections of the skin usually are bacteria or yeast organisms. These can be identified on cytologic preparations and appropriate therapy initiated. Bacterial cultures should always be interpreted in the light of a cytologic evaluation, with multiple types of organisms growing on culture we need to know which one of them is most numerous in the lesions and thus most important to treat!
B. Methods
• Rubbing, or impressing a slide onto a skin surface.
• Inserting a cotton bud in the ears.
• A direct impression technique with clear sticky tape collects the debris from the surface of the skin. The tape is impressed onto the skin (sticky side down) and then laid (also sticky side down) onto a drop of methylene blue or a drop of the blue stain of DiffQuick on a slide (especially useful for Malassezia).
• Aspiration from nodules or abscesses. A a 22 g needle is inserted and redirected through the same insertion point several times in different parts of the nodule. The needle is then withdrawn and needle contents are blown onto a slide. The smear is air dried.
Stain
• Modified Wright’s stains are commonly used. [...]