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Dermatology > Diagnostic Techniques > Flashcards

Diagnostic Techniques Flashcards

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Dermatology Board Prep flashcards
1
Q

Diagnostic Tequniques

(5)

A
  1. Skin scrapings
  2. Wood lamp
  3. Cultures
  4. Patch test
  5. Skin biopsies

*Note: these techniques are not unique to dermatology, family practice can do many of these as well *

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2
Q

Skin Scrapings

(3 uses, 4 stains)

A

Uses:

  • KOH - fungus
  • Tzanck smears - virus (herpes)
  • Scabies - protozoa

Tools:

  1. Microscope
  2. # 15 blade
  3. Glass slide and cover slip
  4. Stains
    • KOH stain = Potassium Hydroxide (add after collecting skin)
    • Tzanck smear = Giemsa, Wrights, or Sedi stains
    • Scabies smear = Mineral Oil, KOH, Saline
      • apply oil to skin prior to scraping to keep scabies in tact
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3
Q

KOH Skin Scraping

A
  • Most sensitive office test, if done properly
  • Identifies
    • Tinea
    • Candida
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4
Q

Scraping, Top of Vesicle

(procedure, purpose)

A

Procedure:

  • lance vesicle
  • insert #15 blad into vesicle
  • scrape bottom surface of the top of the vesicle (celing of carrier dome)

Purpose: KOH prep scraping for tinea

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5
Q

Scraping, leading edge of annular lesion

(procedure, purpose)

A

Procedure: scrape along outside of lesions, towards area of highest proliferation

Purpose: KOH stain for tinea

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6
Q

Scraping, Nails

(procedure, purpose)

A

Procedure: get deep scraping of nail underside

  • clip nail
  • sample “cheesy” substance underneath the clipping
  • if nail is not cuttable, scrape as far as you can s hurting pt or removing nail

Purpose: KOH stain for tinea

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7
Q

Tzanck Smear

(funtion, positive finding)

A

Function: Standard microscopic test for rapid Dx of Herpes infection

  • cannot distinguish b/w herpes types (HSV 1, 2, or VSV)
  • PCR is usually used instead of this

Positive Test:

  • multinucleated giant cells = atypical keratinocytes c large nuclei
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8
Q

Tzanck Smear Procedure

A
  1. Sample appropriate area
    • ​Scrape base of vesicle/bulla (“floor of the carrier dome”)
      • this will hurt the pt a little bit
      • “like spreading peanut butter on break”
    • Sample only fresh lesion
  2. Use # 15 blade to correct area and transfer to slide
  3. Stain
    • ​Giemsa
    • Wrights
    • Sedi stain
  4. Cover c slip
  5. Look for multinucleated giant cell
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9
Q

Scabies Smear

(diagnostic method)

A

Identify Sarcoptes scabiei hominis via microscopic examination

  • female mite
  • eggs
  • fecal matter
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10
Q

Scabes Smear, Procedure

(5 steps)

A
  1. Apply mineral oil to sample area
  2. Sample area in question c # 15 blade
    • ​scrape burrows, vesicles, or papules
      • this is where females live (no males)
    • have pt point to itchiest area c index finger
      • finger webs
      • flexural wrists
      • genitalia
    • ​​use vigorous force, it is okay to cause point bleeding
  3. Coverslip
  4. +/- stain if mineral oil not used
    • ​KOH
    • saline wet mount
  5. Look for
    • ​female mite
    • eggs
    • fecal material

Note: look for fragments as well as whole organisms. scraping may cause trauma to the organism

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11
Q

Woods Lamp Exam

(def, purpose)

A

Def: fluorescing affected area c invisible “black light” (long wave UV radiation)

Purpose: Identify the following pathogens

  1. Tinea capitis (non-T. tonsurans) = yellow - green
  2. Tinea versicolor - dull yellow
  3. Erythrasma - coral red
    • board question
  4. ​Pseudomonas - green
  5. Vitiligo - accentuates epidermal pigment
    • good for level 2 skin
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12
Q

Pearls, Bacterial Cultures

(2)

A
  1. Best yield when infection is superficial
  2. Vigorously swab the area of most inflammation
    3.
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13
Q

Culture Turnaround Times

A
  • Bacterial ~ 1 week
  • Viral ~ 1 week
  • Fungal ~ 3 weeks for DTM, 4 week for Sabouraud’s
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14
Q

Viral Culture Pearls

(2)

A
  1. Keep refridgerated
  2. Best to sample base of fresh vesicle or bulla
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15
Q

Fungal Cultures

(list and describe 2 types)

A
  1. DTM
    • ​identify presence of a deratophyte (nonspecific)
      • test turns red
  2. Sabouraud’s Dextrose Agar
    • ​identify type of dermophyte (specific)

*These are not always done, empiric tx is popular c fungal infection *

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16
Q

Patch Test

(function, procedure)

A

Function: Test of choice to distinguish contact allergic vs. irritant dermatitis

  • Allergic
    • immunologic mediation
    • acquired sensitivity affecting certain individuals
  • Irrirtant
    • not immunologically mediated
    • due to chemical damage to skin

Procedure:

  1. Fill wells c potential allergens
    • standard 50 exist
    • expander packs to accomodate for potential allergens/irritants in pt’s work or home
  2. Apply patches to back for 48 hours
  3. Mark reactive areas and compare c substance in asst well
17
Q

Skin Biopsy

(def, advantage, procedure-general)

A

Def: removal of the skin for histologic examination

Advantage:

  • Best dx technique for cutaneous neoplasms that cannot yield clinical dx
  • Helpful in inflamatory skin disorders of uncertain etiology
  • Skin is always readily available for biopsy

Procedure:

  1. Obtain skin via specific biopsy technique
  2. Submit specimen to pathologist
  3. Receive the following
    • ​Histology and examination (H&E)
    • Specialized studies (not exhaustive list)
      • immunofluorescence
      • electron microscopy
      • culture
      • special stain
      • PCR
18
Q

Culture vs. Biopsy

A

The medium that the sample is preserved/observed in determines culture vs biopsy

19
Q

Types of Skin Biopsy

(6)

A
  1. Curette
  2. Scissor
  3. Shave (most common - 70%)
  4. Punch (most common - 30%)
  5. Incisional
  6. Excisional
20
Q

Curettage Biopsy

(indication, type of specimen, anesthetic, closure)

A

Indication: BCC

Specimen: Fragmented

  • these cells tear away very easily b/c they are not tightly adhered to each other. this is a good historical component to note - bleeding c light rubbing

Anesthetic: Wheal

Closure: Secondary (no stitches)

21
Q

Scissors Biopsy

(indication, specimen type, anesthetic, closure)

A

Indication: pedunculated tumor (stalked c large mass on top - skin tag)

Specimen: tissue above connectionto epidermis

Anesthetic: none or wheal

Closure: secondary (no stitches)

22
Q

Shave Biopsy

(indication, specimen obtained, anesthetic, closure)

A

Indication: superficial process elevated above surrounding normal skin

Specimen: epidermis + superficial dermis

  • Don’t go too deep to avoid distrubing collagen and causing scar

Anesthetic: wheal

Closure: secondary (no stitches)

23
Q

Punch Biopsy

(indication, specimen obtained, anesthetic, closure)

A

Indication: depressed lesion or process primarily in dermis

Specimen: epidermis, dermis, and usually some fat

Anesthetic: wheel and/or deep (usually both)

Closure: Primary simple suture (1 stitch)

24
Q

Incisional Biopsy

(indiation

A

Indication: lesions present in deep SQ fat or in fascia s removing the entire lesion

  • provider inconfidence
  • unknown how much will need to be removed or removal procedure before histological consult

Specimen: SQ fat c overlying dermis and epidermis

Anesthetic: Deep

Closure: Primary layered closure (dermal stitch and close up epidermis as necessary)

25
Q

Excisional in toto Biopsy

(indication, specimen obtained, anesthetic, closure)

A

Indication: lesions not uniform in pathology, biopsy intended to be definitive tx

Specimen: full-thickness skin and SQ tissue via fusiform excision

  • 3:1 ratio - fit 3 lesions into length of elipse
  • orient ellipse c skin lines to avoid hypertrophic scar

Anesthesia: deep

Closure: primary layered closure (dermal and epidermal stitches)

26
Q

Biopsy Site Selection

(name sites for: tumor, blister, ulcerated/necrotic lesions, generalized polymorphous eruption, vasiculitis c purpura, vasculitis c livedo pattern)

A
27
Q

Local Anesthesia Admin Types

(describe 2)

A

a. Subcutaneous infiltration technique: 5-10 min to achieve numbness
b. Dermal infiltration technique to produce a wheal: seconds to achieve numbness

Dermatology (2 decks)

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