TST Interpretation and Classification

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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.