skin tests

The Mantoux tuberculin skin test is one way of finding out whether a person is infected with Mycobacterium tuberculosis, a bacteria known for causing Tuberculosis (TB). 

Procedure

0.1ml of tuberculin purified protein derivative (PPD) will be injected into the inner surface of either forearm. The patient can then return home but should return between 48 and 72 hours. Returning back after 72 hours will result in an invalid test result. 

When the patient returns within 48-72 hours, the skin reaction should be measured in millimetres. The reaction that will occur is called induration (firm swelling). 

Results

1. Induration of 5 or more millimetres is positive for TB if:
   • Recent contact with a person infected with TB
   • Previous TB infection
   • History of organ transplants
   • Immunosuppressed state
   • HIV positive
2. Induration of 10 or more millimetres is positive for TB if:
   • People born in countries where TB disease is common
   • Drugs abuse
   • Mycobacteriology laboratory workers
   • People who live or work in high-risk congregate settings (i.e.: nursing homes, homeless shelters)
   • People with low body weight
   • Children younger than 5 years old
   • Conditions placing them at high risk for TB (i.e.: silicosis, diabetes mellitus, severe kidney disease, etc.) 
3. Induration of 15 or more millimetres is positive for TB if:  
   • People with no known risk factors for TB