Introduction
The Mantoux skin test is also known as the Tuberculin Skin Test. It is a test used to see if your child has been infected with the bacilli germs that cause tuberculosis (TB). It is important to detect TB early so that treatment can be started as soon as possible.
Before the test
The doctor or nurse will provide you with any relevant information before the test. They may ask you about any illnesses, medications or vaccinations that your child has had, or whether they have had TB, or have been exposed to TB in the past.
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. Make sure to ask any questions you have.
During the test
This test involves injecting a small amount of Tuberculin between the layers of the skin, usually on the inside of the left forearm using a small sterile needle and syringe. Tuberculin is a combination of proteins (a purified protein derivative) that react to the presence of TB bacteria by forming a lump in the skin over 2-3 days.
After the test
You will need to bring your child back in to the hospital 2-3 days after the test to have the results checked. If the test is positive, a lump will appear where the injection was made after 2-3 days. The size of the lump will be measured.
If the test is positive, then your child may need to have a chest x-ray and have further follow-up and treatment by a doctor or a nurse.
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
- have been immunised for tuberculosis with the bacillus calmette–guérin or BCG vaccine
- have tuberculosis.
Management
Managing skin during the test
The reaction can get itchy, but it is important to not use any bandages or ointments as this can affect the results. You can encourage your child not to scratch the injection site by wearing long sleeves or jumpers. Scratching the injection site can put your child at risk of developing an infection.
If your child gets blisters around the spot where the injection was given, do not pop or break them.
Your child can do all their normal activities including playing sports, having a shower, and going to school.
False negative
A negative result can be incorrect, also called a false negative, if your child:
- is taking medicine to lower their immunity, like steroids or chemotherapy drugs
- has a viral illness like measles
- has been vaccinated for measles within the last month
- is very sick.
If the test needs to be done again, it will be done on the other arm.