TB Test for Employment & Students
HPD04067TuberculosisSkinTestingQuickReferenceforHe.pdf (hamilton.ca)
Tuberculosis Skin Testing:
Reading of the TB skin test should be performed
by a trained Health Care Professional 48 to 72
hours after injection. If this ‘window’ is missed, the
skin test will need to be re-administered.
1. Inspect and palpate the site:
Under good lighting, inspect the skin test site for
any induration (hard, dense, raised formation)
With your finger tip, determine if any induration
is present.
2. Mark the border for induration:
Mark the edges of induration by moving the tip
of a pen at a 45o
angle laterally toward the site
of the injection. The tip will stop at the edge of
induration if present.
3. Measure the induration:
Using a calliper ruler, measure the distance
between the pen marks.
Measure induration – NOT erythema / redness
4. Record the induration in millimeters (mm)
Do not record the result as “positive” or
“negative”. Results should be recorded in mm
of induration.
If there is no induration, record as 0 mm.
Reading a TB Skin Test
Monitor the client for 15 minutes post injection
for signs of allergic reaction. Instruct them to
return in 48-72 hours to have the test read.
1. Locate the injection site:
With the forearm palm side up select an area 5 to 10
cm below the elbow that is free of tattoos, scars or
broken skin. If neither forearm is suitable, use the
outside of the forearm or upper arm.
Clean the site with alcohol and allow it to dry.
Do not use local anesthetic cream (e.g. EMLA cream)
as 10% of those applying this cream report localized
edema, which could be confused with a positive TST
result.
2. Prepare the Tuberculin:
Check the tuberculin expiration date and the date that
it was opened; once opened discard after 1 month.
With a 1mL Tuberculin syringe with a ½ inch, 26 or 27
gauge needle, withdraw 0.1mL (5 tuberculin units).
Administer tuberculin immediately after it is drawn.
3. Inject the Tuberculin
While holding the skin taut, insert the needle with the
bevel up just below the skin’s surface at a 5o
-15o
angle. The tip of the needle will be visible just below
the skin.
Inject the tuberculin.
4. Check the injection site
Look for a pale elevation in the skin (wheal) that is 6-
10 mm in diameter. If no wheal appears, repeat the
injection on the opposite forearm or at least 10cm
away from the previous site.
Instruct the patient not to scratch the site and do not
cover it with a band-aid.
5. Document the Test
Record the date and time of test, Tuberculin lot
number and expiration date, dose of Tuberculin
injected and the site(s) of injection.
The following persons should not receive a TST:
Documented history of treatment for Active TB
disease or Latent TB Infection
History of severe blistering reactions to previous
TST
Extensive burns or eczema over testing sites
Patients with major viral infections or live-virus
vaccinations in the past month i.e., MMR,
Varivax, Yellow fever
Contraindications
Storage of Tuberculin
Store Tubersol in the refrigerator between 2o
C and 8o
C – do not freeze.
Store and transport in the dark and avoid exposure to light to ensure potency and
accuracy of the solution.
Record on vial the date it was opened; vials should be discarded if they have been
open for more than 30 days or if the expiration date has passed.
Administering a TB Skin Test
Tuberculosis Skin Testing: (continued)
If you have any questions, please contact the
TB Control Program at: 905-540-6636
Interpreting a TB skin test
www.hamilton.ca/tuberculosis
What to do following a Positive Skin Test
Reporting Requirements
All persons with a positive skin test must be
reported to Public Health within 7 days. All
suspect and active cases must be reported
within 24 hours.
Two-Step TB Skin Testing
How to do a 2-step Skin Test
Tuberculin
Reaction
(mm of
induration)
Skin Testing for Contacts of
an Active TB Case
Hamilton Public Health Services
TB Control Program
General Inquiries…………… 905-540-6636
Reporting Fax………………..905-546-4841
TB Clinic
Charlton TB Clinic…………..905-522-1155 x 34198
If the TB skin test is positive, the client should be
evaluated further to rule out active TB disease:
medical evaluation of risk factors for TB and
presence of symptoms
Chest radiography
In presence of symptoms, test sputum for acid fast
bacilli smear and culture.
A single TST may elicit only a little response yet
stimulate an anamnestic immune response. A 2-step
process will stimulate the immune response, and a
positive reaction may occur when a person is retested
1 to 4 weeks later. This delay response is called a
booster phenomenon.
A 2-step skin test assists in establishing a true
baseline result for people who will be getting serial skin
tests.
If a baseline is not measured through 2-step skin
testing, a positive skin reaction on subsequent tests
may be interpreted as a conversion (i.e. TB infection),
when in fact the positive skin reaction may an old
infection.
2-step skin tests should be done on persons who:
o may require subsequent testing (e.g. health
care / correctional workers)
o are becoming residents in a long-term care
facility / retirement home / group home
o are traveling to a TB endemic country for a
month or more.
Setting in which reaction considered
significant
(meaning probable TB infection)
0-4 – HIV infection* with immune suppression
AND the expected likelihood of TB infection
is high (e.g., patient is from a population with
a high prevalence of TB infection, is a close
contact of an active contagious case, or has
an abnormal x-ray)
5-9 – HIV infection*
– Close contact of active contagious case
– Children suspected of having TB disease
– Abnormal chest x-ray with fibronodular
disease.
– Other immune suppression: TNF-alpha
inhibitors, chemotherapy
≥ 10 – All others
*All clients with HIV are high risk and should be
referred to a TB specialist.
BCG Vaccination Considerations
BCG vaccination can be ignored as a cause of a positive
TST if:
BCG vaccine was given in infancy, and the person
tested is now >10 years of age.
o Have traveled to or resided in an TB endemic
country for more than 1 month.
TB Contacts are identified by Public Health and
provided with documentation for further follow-up
from their physicians.
Skin tests for contacts of active TB cases are covered
by OHIP.
1. Administer and read the initial TB skin test.
2. If reaction on the first skin test is positive, a
second skin test should not be administered.
3. If the first skin test does not meet positive criteria,
administer a second skin test 1-4 weeks later.
4. Document both skin test results. All subsequent
testing requires only a single test.
References: Canadian Lung Association (2007). Canadian Tuberculosis Standards (6th
ed.) Ottawa: Canadian Lung Association Updated June 2012
There is a high probability of TB infection: close contacts
of an infectious case, Aboriginal Canadian from a highrisk community, or immigrants/visitors from a country
with high TB incidence.
There is a high risk of progression from TB infection to
disease.
Answer 10
Do you have any questions?
Call us and request an appointment with our doctors in Gage Medical Center.