TB blood test (QuantiFERON) in Chiswick

What the test measures

Tuberculosis (TB) is a bacterial infection that mainly affects the lungs. Many people who breathe in the bacteria never become ill, because the immune system keeps the infection contained. This is called latent TB. It is not infectious, but it can become active later, particularly if the immune system is weakened.

The QuantiFERON test is an interferon gamma release assay (IGRA). Your blood is mixed in the laboratory with proteins specific to the TB bacteria, and the test measures whether your immune cells respond by releasing interferon gamma. Unlike the older skin test, it is not affected by previous BCG vaccination. NICE guidance supports IGRA testing for latent TB in many situations.

The price includes the sample taken at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result, and a GP feedback report on request.

Who it is for

• Your employer, especially in healthcare, requires TB screening.
• You are starting a course, placement or visa process that asks for a TB test.
• You have been in close contact with someone diagnosed with TB.
• You are about to start a medicine that suppresses the immune system, such as a biologic, and need latent TB checked first.
• You have lived in or travelled for long periods to a country where TB is common.

Understanding your result

A negative result means no immune response to TB proteins was detected. Very recent exposure may not yet show, and people with weakened immunity may not respond, so a repeat test may be advised in some situations. A positive result suggests TB infection at some point, but it cannot tell latent from active TB.

If your result is positive, you will usually be advised to see your GP or a TB clinic for a chest X-ray and assessment. An indeterminate result means the test could not give a clear answer and may need repeating. In every case the result is a starting point for discussion, not a diagnosis.

Preparing for your test

Fasting is not necessary for this test. Please let us know about any steroids, biologics or other medicines that affect the immune system, and whether you have had a TB skin test recently. If you have a persistent cough for more than three weeks, night sweats, fever or weight loss, see your GP rather than booking a screening test.

If you are completing occupational health checks, our infection and immunity tests, including measles, mumps and rubella immunity, are also available. See every blood test and price in Chiswick.

Questions

How much is a TB blood test in Chiswick?

The TB Blood Test (QuantiFERON) costs £89. It includes the blood sample at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result, and a GP feedback report on request.

Will my BCG vaccine affect the result?

No. QuantiFERON uses TB-specific proteins that are not found in the BCG vaccine, so previous vaccination should not cause a false positive.

Does a positive result mean I have active TB?

Not necessarily. Many people with a positive result have latent TB, which is not infectious. A chest X-ray and clinical assessment are needed to tell the difference.

How long after contact with TB should I test?

The immune response can take up to around eight weeks to develop after exposure. Your practitioner or local TB service can advise on timing.