Tuberculin skin testing
Andrea Jurgrau, CPNP
Joan Coetzee CPN, PN
for the P1078 team
CDC TST guidelines
P1078 uses CDC guidelines for TST
The guidelines can be found at the
CDC website, as can training material
The P1078 MOP has an overview of
What is a TST?
A tuberculin Skin Test (TST)
The technique we are using in the Mantoux
This is a intradermal injection of Protein
Purified Derivative (PPD)
It tests for exposure to Tuberculosis (TB)
also known as latent TB
Because it is a delayed immune response, it
takes 48-72 hours for the reaction to take
place and the TST to be read and
Materials for administering
PPD 5tu* unit dose vials for intradermal
Single use, disposable TB syringe and ½
inch 27 gauge short bevel needle.
Tuberculin skin test ruler (plastic ruler with
Refrigerator for long-term storage at 2-8
degrees C and a cooler for use in the clinic
if vial can’t be returned to refrigerator
Preparing to Place TST
Wash hands and put on gloves. If no water is available, use an appropriate skin-
cleaning product (e.g., an alcohol based hand cleaner).
Check PPD vial’s expiration/opening date. If it has been open for more than 30
days, discard the vial and get a new one. Be sure you review proper storage for
vials between use.
Place patient’s arm on a flat surface, exposing the volar (inside) surface of the
Locate site for the injection (2-4 inches below elbow, where no scars, bumps or
veins are located).
Clean the injection site with an alcohol swab and allow it to dry before applying test.
Wipe the top of the PPD vial with a second alcohol swab and place the vial on a flat
Prepare the syringe by inserting it into the vial. Inject 0.1 ml of air into the airspace
in the vial. Do not inject air into the PPD solution.
Invert the vial, keeping the needle tip below fluid level.
Pull back on the plunger of the syringe and draw slightly more than 0.1 ml of PPD
Remove the syringe from the vial and tap the syringe lightly to dispel air bubbles.
Hold the syringe point up and expel air and/or excess fluid, leaving exactly 0.1 ml of
PPD solution in the syringe.
Return the PPD vial to the refrigerator when not in use and place on a cooling pad
when in use. Protect the vials from light.
NOTE! interferon gamma blood collection has to happen first before
TST placement for P1078
Stretch the skin of the injection site with the thumb of the non-dominant
hand (e.g., left hand for right-handed persons).
Hold the syringe between the thumb and forefinger of the dominant hand,
(e.g., right hand for right-handed persons) with the bevel of the needle
pointing upward. Insert the needle intradermally (just under the top layer
of skin) at a 5°-15° angle, with the bevel up. The bevel should be just
below the skin, and the needle should be inserted about 3mm so the
entire bevel is covered.
Release the stretched skin, inject the PPD solution slowly. A firm
resistance should be felt as the tuberculin solution enters the skin.
Remove the needle from the injection site (DO NOT RECAP). Discard the
syringe immediately in a sharps container.
Measuring TST after Placing
Once you place the TST you must
measure it right away to make sure it
was done properly
Use your ruler to measure the wheal.
It should be at least 6mm in diameter.
If it is not, repeat the TST at a new
site at least 2 inches away from first
site. Be sure you document the test
TST Patient Teaching
Educate the patient on the possible reactions to
the TST (e.g., mild itching, swelling, irritation).
Instruct patient not to rub, scratch or put an
adhesive bandage or lotion on the test site. The
area may be washed and patted dry.
Document the test in the patient’s CRF (including
second test if done). Be sure to include location of
test site in your documentation.
Schedule reading date and explain the importance
of the patient returning for reading in 48 to 72
Materials for reading TST
Tuberculin skin test ruler (plastic ruler
with mm rule.)
Alcohol pads to remove pen marks
Read the result 48 to 72 hours after administering the test.
Inspect the injection site for raised areas.
Palpate the arm for a hard, raised area known as an induration.
Feel the edges of the induration with the index finger
Mark the 2 edges of the induration with a dot, using a black,
watermark or felt-tip pen.
Measure the induration (not redness) at its widest point
transversely, from 1 marked edge to the other, using a flexible
TST ruler. If the reading is between 2 points, the lower value
should be used. Swollen areas, if they feel hard, (but not red
areas) should be palpated and included in the measurement.
Record the size in millimeters and not simply as “positive” or
“negative”. If there is no induration, record the result as “00 mm.”
Interpret the reaction as positive or negative based on the size of
the induration being ≥5mm (for HIV+ study subjects)
Explain the meaning of a positive or negative reaction to the
individual and refer for follow-up evaluation, if needed.
Vaccination with live attenuated viral
vaccines such as measles, mumps and/or
rubella (MMR) can cause a false-negative
reaction to the TST. The TST can be
administered on the same day as the live
vaccine. If a skin test is needed, and was
not given in conjunction with the
vaccination, wait 4-6 weeks before
administering a TST.
If the patient fails to return for the scheduled
reading but returns up to a week (7 days) after
the test, examine the test site and measure
any induration present; if it is large enough to
be classified as positive, record the result. No
further testing is needed. If there is no
reaction, or the induration is too small to be
classified as positive, repeat the test. A
repeat test can be given immediately.