What amount of serum is present in a purified protein derivative (PPD) tuberculin skin test?

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Last updated: October 16, 2026 • View editorial policy

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PPD (TST) Dose and Volume

  • Bold recommendation: Administer exactly 0.1 mL intradermally, containing 5 tuberculin units (TU) of PPD. 1, 2

  • Practical details

    • Use Mantoux method on the forearm with a tuberculin syringe; expect a 6–10 mm wheal if placed correctly. 2
    • Do not transfer PPD between containers; use promptly after drawing to avoid potency loss. Refrigerate vials, protect from light. 2

  • Nuances and pitfalls

    • “5 TU” refers to biologic potency equivalent to 5 TU of the PPD-S standard in 0.1 mL; other strengths (e.g., 1 or 250 TU) are not routinely used or standardized. 2
    • Underdosing (<0.1 mL) or subcutaneous injection can yield false results and impact patient outcomes (missed LTBI increases future TB morbidity/mortality). Ensure correct intradermal technique. 2

References

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