American Medical Certification Association (AMCA) Phlebotomy Practice Exam

What is the most common method used to administer a TB test?

1. Orally

2. Intramuscular injection

3. Injecting a TB antigen under the skin

4. Subcutaneously

The correct answer is: Injecting a TB antigen under the skin

The most common method used to administer a TB (tuberculosis) test is through injecting a TB antigen under the skin. This method, known as the Mantoux test or tuberculin skin test, involves placing a small amount of purified protein derivative (PPD) just beneath the skin's surface, typically on the forearm. The immune response to this antigen is then assessed after 48 to 72 hours by examining the area for any induration, which indicates a reaction to the TB antigens. This approach is specifically designed to evaluate whether an individual has been exposed to the bacteria that cause TB and is the standard practice in various healthcare settings. Other methods of administering medications, such as orally or intramuscularly, are not used for the TB test due to the need for a localized immune response check at the injection site. Subcutaneous injections, while similar to the method used for a TB test, are not the standard for this specific examination, as the precise subdermal placement of the PPD is crucial for accurate results.