The skin test for tuberculosis is also known as the Matoux or tuberculin test. This test measures the immune system's response to the beating that causes TB. The result will be interpreted and reported by a doctor within a couple of days of execution. This article tells you how to read tuberculin.
Steps
Step 1. Go to your doctor to undergo the examination
You will be given an injection of purified tuberculin protein derivatives. A swelling will form at the injection site which will disappear within a couple of hours.
Step 2. Do not bandage your arm for 48-72 hours as directed by your doctor
You can wash and dry your arm, but very carefully.
You shouldn't even scratch or rub the affected area. If you feel itchy, apply a cold washcloth
Step 3. Go back to the doctor within 72 hours of your test being read
If you do not show up within this time, the exam is invalidated and you will have to repeat everything from the beginning.
Step 4. Measure the size of the wheal at the injection site
(Do not confuse wheal with swelling. The first is a hard, dense, raised deformation with defined edges.) The measurement will be in millimeters.
Step 5. Compare the size of the wheal to the standard ones for risk identification
Here's how to interpret them:
- A wheal of 5 mm or more is categorized as positive in individuals with HIV, in transplant patients, with chronic diseases (rheumatoid arthritis), in individuals who have been in contact with TB patients or who have a radiological picture compatible with the infection.
- A wheal of 10 mm or more is considered positive in people who have recently visited countries where TB is present, in those who use intravenous drugs, in healthcare workers, or in children / adolescents who have been in contact with adults such as high risk.
Step 6. A wheal of 15 mm or more is considered positive in all individuals regardless of their risk factor
The test is reported as positive even if there are blisters and swelling.
Step 7. Undergo other tests if your doctor judges your test positive or borderline
Advice
Use a ballpoint pen at an angle of 10 ° to the skin. Slowly push from the outside of the wheal and swelling towards the center of the same until the pen stops on a hard lump. Mark the point and repeat for the other side
Warnings
- There can be both false positives and false negatives with this test. If you are unsure about your TB test results, consult with your doctor as soon as possible.
- A TB test should always be interpreted by a licensed physician within a maximum of 72 hours. A doctor possesses the knowledge and skills necessary to understand the results correctly.
