OD 29 - Special investigations in oral medicine Flashcards
Why is skin patch testing used?
To test for type 4 mediated hypersensitivity reactions
What is exfoliative cytology?
Exam where cells are scraped from lesion or material from cyst to detect virally damaged cells/ pemphigus/ candida hyphae
What are the pros and cons of exfoliative cytology?
+ Quick, easy, no LA
- unreliable for cancer diagnosis and frequent false results
When is an intra-oral biopsy indicated?
Neoplastic/premalignant features
Persistent lesions with unknown cause or unresponsive to tx.
What 2 mucosal biopsy are most common?
Incisional and excisional (rare)
What is the procedure for a simple incisional biopsy?
Don’t inject LA in lesion or apply pressure (damage tissue)
Include some healthy tissue
Adequate depth to see interface between epithelium and connective tissue
4-5mm
Place sample in 10% formalin solution
Suture area
What is the difference between 1.direct and 2.indirect immunofluorescence?
Process of labelling antibodies/antigens with fluorescent dye
- Detects any in situ deposition of immunoglobulins
- Detects any circulating autoantibodies (i.e. in blood)
What is the process of direct immunofluorescence?
One stage
Perilesional sample (within 1 cm of lesion) - as inflammatory cells in lesions can destroy immune deposits causing false results
Frozen immediately then cut into thin sections
Mostly tests for human IgG, IgM, IgAm complement component 3 and fibrinogen - showing green fluorescence under UV
Results –> type, number, location and immunomorphology
Why are punch biopsy not a preferred choice?
Twisting motion can dislodge the epithelium
What is the process of indirect immunofluorescence?
2/more stages Need serum (from pt.) and tissue substrate (not from pt.) 1st stage = incubate patients serum with normal substrate 2nd stage = exposition of substrate to fluorescence
When is the salt-split skin technique used and how is it carried out?
For sup-epidermal blistering diseases
Split skin made by 48-72hrs in 1M NaCl
