Diagnostic Approaches to Skin Disease Flashcards
Considerations for diagnostic testing
Prioritise which tests will help you narrow down differentials
Take an adequate number of good quality samples
Examine efficiently
Be aware of limitations
* False positives
* False negatives
Diagnostic tests for ectoparasites
Coat brushing
Unstained acetate tape
Skin scrapings (deep and superficial)
Trichograms
Diagnostic tests for bacteria
Cytology
Microbial swab for culture
Diagnostic tests for fungi
Trichograms (dermatophytes on shaft)
Cytology (yeasts)
Wood’s lamp (Microsporum canis)
McKenzie coat brush (dermatophytes for culture)
Microbial swab for culture (yeasts)
Skin surface cytology tests
Used to visualise cells and microbes on skin surface
* Direct impression smear
* Cotton bud impression smear
* Acetate tape strip
Type of lesion for direct impression smear
Most/greasy lesions
Ruptured pustule
Skin under crusts
Accessible sites
Type of lesion for cotton bud smear
Ear canals
Type of lesion for stained acetate tape strip
Dry lesion
Less accessible locations
Staining for direct impression smear
All 3 diff quick solutions
A - Fixative
B - Eosin
C - Methylene blue
Dip method
Staining for cotton bud smear
All 3 Diff-quick solutions
A - Fixative
B - Eosin
C - Methylene blue
Rack method
Staining for acetate tape strip
Only B and C
*Dip method
Or C only
* Pipette
Fine needle aspirate cytology
To visualise skin cells below surface
Eosinophil granule colour using H&E stain
Pink - Eosinophilic
Neutrophil granule colour using H&E stain
Granules don’t stain
Basophil granule colour using H&E stain
Dark blue - Basophilic