Spectrum: Local Antimicrobial Stewardship, for UCLA Health

Tuberculin Skin Test

Definition

No longer routinely offered on inpatients, except in specific populations.

Intradermal injection of purified protein derivative (PPD) and measurement of induration diameter in 48-72 hours for diagnosis of latent TB infection (also positive in most active TB cases).

Criteria for a positive test are:

  • ≥ 5mm - high risk of developing active TB (e.g. HIV, close contact of TB case, immunocompromised)

  • ≥ 10mm - other risk factors for TB infection (healthcare worker, IV drug use, diabetes)

  • ≥ 15mm - no risk factors for TB