I had the BCG vaccine. Will that make it positive?

No, and that is the main reason to choose this over the skin test. The proteins used are absent from the BCG strain, so a vaccination scar does not produce a false positive the way it does with a tuberculin skin test.

Do I have to come back to have it read?

No. That is the other advantage over the skin test, which has to be read 48 to 72 hours later. This is one blood draw, and the result comes from the laboratory.

What happens if it is positive?

A positive result means you have been infected at some point, not that you are ill. The next step is usually a chest X-ray to rule out active disease, and then a discussion about treating the latent infection — which is a course of medication, not a hospital matter.

Is it accepted for immigration medicals?

Interferon-gamma release assays are widely accepted, but requirements differ by programme and change over time. Bring the paperwork you were given so the right test is ordered for the right purpose.

Four collection tubes with grey, green, yellow and purple caps in a brass rack on marble.

Lab and screening · Reviewed by a physician

Tuberculosis screening — QuantiFERON-TB Gold

Latent tuberculosis is an infection your immune system has contained but not cleared. It causes no symptoms and can reactivate years later. This blood test detects it in a single visit, and a previous BCG vaccination does not affect the result.

From$450per test

Book an evaluation See how it works

At a glance

Appointment

15minutes

Review, then a blood draw.

Sample

Blood

Blood, from the arm.

Result

3–7days

One visit, no return for reading.

Preparation

None

No preparation needed.

A single cream form face down with a brass clip at its corner.

What it looks for

What this test answers.

A test is only worth doing if you know in advance what you would do with each possible answer.

How it works

It asks your white cells if they remember.

The test mixes a sample of your blood with proteins found in Mycobacterium tuberculosis. If your immune system has met the bacterium before, the T-cells in that sample recognise the proteins and release interferon-gamma, which the laboratory measures. No recognition means no release, and a negative result.

The advantage over the old skin test is which proteins are used. They are present in tuberculosis but absent from the BCG vaccine strain and from most environmental mycobacteria — so a BCG scar on your arm, which made skin tests ambiguous for millions of people, does not make this one positive. It also needs one visit rather than two, because nothing has to be read off your skin 48 hours later.

Three empty glass tubes with grey caps in an oak rack.

01
The sample
Taken at the clinic, labelled against your file, and sent to an accredited laboratory.
02
The analysis
The laboratory runs the assay and reports the result back to the physician who ordered it.
03
The explanation
You are told the result and what it means for you, whichever way it comes back.

Your visit

One appointment, then the result.

The appointment is short. The part that matters is what happens with the result.

01
First
The review
Why the test is being done — immigration, employment, contact or before immunosuppression — and whether any symptoms change what is needed.
02
Then
The sample
A standard blood draw into specialised tubes that must reach the laboratory within a set window.
03
Afterwards
The result
The physician reviews it against your history and tells you what it means and what follows.

Dr. Andrew Gyopar, physician at Clinique Medix.

Who performs it

A physician orders it and reads it.

A result on its own is a number. What makes a test useful is a physician who ordered it for a reason, reads it against the rest of your history, and tells you what it means and what happens next — including when the answer is that nothing needs to happen.

Dr. Andrew Gyopar

General Surgeon, Medical Director

Pricing

The price, agreed before anything starts.

What it costs, and what the figure is counted in. The plan and the price are written down and agreed at your evaluation, before any treatment begins.

From

$450per test

One blood draw, one result. No second visit is needed to have it read.

Ordered and reviewed by Dr. Andrew Gyopar. Laboratory analysis is carried out by an accredited external laboratory.

Prices are before taxes and may change without notice. Results vary from one person to another. A medical evaluation is required before any treatment.

Book an evaluation

Before and after