Tb Testing Flashcards
What is BCG?
Is it effective?
Side-effect?
Bacille-Calmette-Guerin vaccine for TB
It is not 100% effective
Causes false positive reactions to TST
What is the test agent for TST?
Storage requirement?
Dose?
Mammalian Old Tuberculin (MOT)
Must be refrigerated until used
0.1mL ID
Where is the testing location?
Why this site?
Upper eyelid just above the eyelashes
Easily observed location in unsedated monkeys
How is the test read?
Read at 24, 48, & 72hr post injection
Eyelid is evaluated for redness, bruising or swelling
Reactions are graded on a scale of 1-5 depending on severity
Describe grades 1 through 5
- Grade 1 -slight bruising of eyelid (negative)
- Grade 2 -erythema of eyelid without swelling (negative)
- Grade 3 -varying degrees of erythema with minimal swelling (indeterminant)
- Grade 4 -obvious swelling with drooping of eyelid (positive)
- Grade 5 -marked swelling and/or necrosis of eyelid; eyelid closed (positive)
Grade?
Interpretation?
Possible Grade 1
NEGATIVE
There is some very mild redness at the test site & no swelling
Grade?
Interpretation?
Grade 1
NEGATIVE
Marked bruising associated with the test site, but no swelling
Often due to injection trauma
Grade?
Interpretation?
Grade 2
NEGATIVE
Pronounced redness of the eyelid, spread beyond the injection site, NO swelling
Grade?
Interpretation?
Grade 3
INDETERMINANT
Slight swelling and drooping of the eyelid +/- erythema
Repeat TST on opposite eyelid
Consider PRIMAGAM or Stat-Pak testing
Grade?
Interpretation?
Grade 4
POSITIVE
Marked eyelid droop due to swelling +/- erythema
Grade?
Interpretation?
Grade 5
POSITIVE
Eyelid is swollen shut with epiphora present
Name 3 reasons for a false-negative TST
- Early in disease course or later in advanced dz
- Treatment with Isoniazid (Tb Tx drug)
- Concurrent immunosuppression (e.g. SIV, Measles)
Name three reasons for false-positive TST
- Prior exposure to Freunds complete adjuvant
- Improper TST administration
- Non-specific reation to vehicle in MOT
