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The page below is a sample from the LabCE course Tuberculosis Awareness for Health Care Workers. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Tuberculosis Awareness for Health Care Workers (online CE course) »

TST Interpretation and Classification

The TST interpretation depends on the measured diameter of the induration and the clinical status of the patient.
  • An induration of 15 or more millimeters is considered positive in all persons.
  • An induration of 10 or more millimeters is considered positive in patients in the high-risk progression groups and in mycobacteriology laboratory workers.
  • An induration of 5 or more millimeters is considered positive in the high-risk infection groups.