The Mantoux (pronounced Man-too) skin test is used to see if your child has been infected with the germs (bacilli) that cause tuberculosis (TB). It is important to detect TB early so that treatment can be started as soon as possible.
How is the test done?
This test involves injecting a small amount of Tuberculin (Purified Protein derivative which is not infectious) between the layers of the skin, usually on the inside of the left forearm using a small sterile needle and syringe.
Results of the test
A positive reaction is measured by the size of the lump (induration) that forms where the injection was put into your child’s arm. This lump occurs over the next two to three days.
Your child may have a positive skin test reaction if they:
- Have had tuberculosis before and have been cured.
- Have been exposed to the tuberculosis bacteria and are well or have been immunised for tuberculosis (BCG).
- Have tuberculosis.
A negative result may actually be incorrect (false negative) if your child:
- Is taking medicine to lower their immunity e.g. steroids or chemotherapy drugs.
- Has a viral illness e.g. measles
- Has been vaccinated for measles within the last month.
- Is very sick.
After the test
If your child has a Mantoux test, you will need to bring them back in two or three days to have the result of the test checked. The reaction can get itchy but scratching the test site may cause an infection, so it is best to encourage your child not to touch it. Bandaids, bandages and ointments can affect the test results, so it is important to keep the skin clear and uncovered (long sleeves and jumpers can be worn). If your child gets blisters around the spot where the injection was given, do not break them.
Your child can do all normal daily activities e.g. playing sports, having a shower, going to school. If you know your child has had a positive Mantoux test before or has been immunised for TB please let the person doing the test know. If you have any questions ask the person who is doing the test.
If the test is positive then your child may need to have a chest X-ray and see a doctor or a nurse.
- A positive result does not always mean your child has tuberculosis.
- It is important to detect TB early to start treatment.
- A Mantoux test is safe.