A mantoux test is a skin test that uses PPD (purified protein derivative) to test if someone has ever been exposed to tuberculosis (TB). A PPD sample is injected subdermally in the anterior forearm, in 48 hours the person returns to the provider to have the test read. If the area of induration is more than 5 mm (measured) they are said to have a positive test result. Protocol for a positive PPD is a chest x-ray. The chest x-ray will either confirm the presence of TB or it will be unremarkable. Even if the chest x-ray is negative some health care providers prescribe anti tubercle medications. (just to be on the safe side).Note that if a positive result is noted this does NOT mean that the person has TB. What it does mean is that either the person is allergic to the PPD or at some point in the past they have come into contact with someone that had TB.