Tuberculin Skin Test Procedure

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The page below is a sample from the LabCE course Latent Mycobacterium tuberculosis Infection and Laboratory Test Methods. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Tuberculin Skin Test Procedure

Note: This synopsis is intended to provide a basic understanding of the TST procedure; to provide greater detail is beyond the scope of this course.
  1. The standard TST is performed using the Mantoux technique, where 0.1 mL of 5 tuberculin units of tuberculin purified protein derivative (PPD) is injected intradermally (into the top layers of skin) on the forearm (also known as the volar surface) using a 27-gauge needle and a tuberculin syringe.
  2. Trained providers read the skin test after 48–72 hours.
  3. The presence or absence and the diameter of induration (hard bump) are measured in millimeters.
Figures 6 and 7. Clinical testing guidance for tuberculosis: Tuberculin skin test. (2025). Centers for Disease Control and Prevention. https://www.cdc.gov/tb/hcp/testing-diagnosis/tuberculin-skin-test.html

Figure 6. Administering the TST
Figure 7. Reading the TST