Immediate Skin Test Flashcards
Type on Gel and Coombs
Type I
Type I vs Type IV
Type I - IgE mediated
Type IV - T cell mediated
contraindications to Type I Skin Test
Severe asthma attack in past two weeks antihistamines pregnancy longtime steroid use beta blockers certain chronic medical conditions
Prick Advantage
Safer than ID Minimal systemic absorption faster less tedious for tech Less discomfort for patient
Disadvantage of skin prick test
cross contamination
cross reaction
Prick Skin Test Positive Control
Histamine 2.75mg/mL
Prick Skin Test Negative Control
Diluent used in extract
- HSA
- Glycerin
Extract Strengths prick test
10,000-20,000 pnu/mL
1:10 or 1:20 w/v
Types of prick device
Dermapick (plastic)
Quintip (metal)
How long after skin test do you read?
15 minutes
Dermapick vs Quintip placement
Dermapick - 45 degress
Quintip - 90 degress
how is prick skin written
wheal x flare by widest size
What is often considered postive on test?
3mm +
Must be determined by physician
What if negative control has wheal and flare of 3mm?
adding requirement that allergent test have wheal size of 3mm more than negative control
false postive reactions
technician error
- excessive strength of antigen admin
- excessive dose
- cross contamination
dermagraphic skin
false negative reactions
improperly prepared/stored extract
patient took antihistamines
technician error - improper placement
intrinsic factor (leather skin)
ID Advantages
more sensitive
less chance of cross contamination
ID disadvantages
more dangerous
more discomfort to patient
more tedious for technician
more irritant/specific reactions
extract strength ID
100-1000 pnu/mL
1:500 or 1:1000 w/v
Positive control ID
histamine .275 mg/mL
Negative control ID
Diluent used in extract
- Saline with HSA
- Saline with Phenol
Location of prick
Forearm
back
location of ID
Upper arm - from bend of elbow to middle of deltoid
forearm
back
ID Procedure
Draw up .05mL and inject .02mL under skin
inject enough for 2mm bleb
