Testing

TST False Negative Reactions

A false negative reaction is no induration after a TST even if the person is infected with Mycobacterium tuberculosis. Some causes of this are:

  • weakened immune system,
  • recent, old or overwhelming TB infection,
  • immature immune system (<6 months of age),
  • some viral illnesses,
  • recent live-virus vaccinations,
  • incorrect TST administration or interpretation.

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