Final answer:
The Mantoux skin test or PPD test for tuberculosis must be read within 48 to 72 hours to assess for a positive reaction, which is indicated by redness, swelling, or hardness at the injection site.
Step-by-step explanation:
When the Mantoux skin test, also known as the PPD test, is administered for the detection of tuberculosis (TB), it involves an injection of tuberculin protein derivative under the skin. This injection should create a small, raised area, known as a wheal. It is important to return within a specific time frame to have the results properly interpreted.
The test must be read within 48 to 72 hours after the injection to assess the response. If read too early or too late, the results may not be accurate. A positive reaction is typically indicated by a degree of redness, swelling, or hardness at the injection site, and the size of this area is measured to determine if TB infection is present. If it's larger than a certain size, based on risk factors, it's considered positive. The exact size for a positive result can vary depending on the individual's risk factors for TB infection.