Tuberculosis Skin Test in South Shore, Montreal
The tuberculosis skin test (TST, also called Mantoux or PPD) at Clinique Revive is a small intradermal injection that screens for prior exposure to Mycobacterium tuberculosis. It is most often requested for school, healthcare employment, daycare or volunteer work, or before international travel or immigration.
The test requires two visits — one for the injection, and a second 48 to 72 hours later for a clinician to read the reaction. Patients across the Rive-Sud often choose private testing because public-system timing is harder to schedule around the strict 48–72 hour reading window.
Two visits, fixed timing
Visit 1: small forearm injection. Visit 2: 48–72 hours later for the reading.<br><br>Both are required.
Trained reading
Reading the induration (the raised bump, not redness) requires a trained eye — a self-read is not reliable.
Documentation provided
A signed result form is provided for school, employer, or immigration purposes.
When a Tuberculosis Skin Test is required
TB testing is commonly required for healthcare workers, students entering clinical placements, daycare staff, immigration applications, certain travel destinations, and people with known exposure. It is also reasonable for people from regions with higher TB prevalence who have not been previously screened.
A skin test is not appropriate for someone with a documented prior positive TST — that population needs a chest X-ray and clinical assessment instead. Patients with active TB symptoms (chronic cough, weight loss, night sweats, hemoptysis) need clinical evaluation, not a skin test.
What to know before the test
Tell the clinician if you have ever had a positive TB test, BCG vaccination, recent live-virus vaccinations (MMR, varicella — these can interfere with TST results within four weeks), or a history of skin conditions on your forearms. Plan your second appointment before leaving the first — the 48–72 hour window is firm; reading earlier or later than that produces unreliable results.
Avoid scratching, covering with bandages, or applying creams to the test site.
What the reading means
The clinician measures the diameter of the induration (the firm raised area, not the redness) at the second visit. Interpretation depends on context: induration cut-offs differ for healthcare workers, immunocompromised patients, recent contacts, and the general population.
A positive reading does not mean active TB — it means prior exposure. Follow-up may include a chest X-ray, IGRA blood test (such as QuantiFERON), or referral.
A negative reading in someone with high suspicion may need follow-up testing.
- Health card or ID
- immunization records (BCG, recent MMR/varicella)
- any prior TB test results
- the form your school/employer wants signed
Registered nurse for both injection and reading
Visit 1: ~15 minutes. Visit 2: ~10 minutes for the reading
South Shore, Montreal, Léry, Candiac — and across the South Shore (Rive-Sud)
Frequently Asked Questions
Why do I need to come back at exactly 48 to 72 hours?
The skin reaction develops over that window. Reading earlier underestimates it; reading later — past 72 hours — also reduces accuracy.
The window is firm.
I had a BCG vaccine as a child. Will my test be falsely positive?
BCG can cause a positive TST, particularly if given recently. The clinician interprets the reading in context; an IGRA blood test is sometimes preferred in BCG-vaccinated people.
What if I miss the reading window?
The test must be redone — there is no way to read a TST after 72 hours. Plan the timing carefully when booking.
Is the injection painful?
It is a very shallow injection just under the skin. Most people describe it as a small sting, similar to a TB skin test in any setting.