Tough training rules for TB skin tests

CDC hopes to avoid common mistakes

Effective tuberculin skin testing relies on the proper administration of the test.

That is why new rules on training those placing and reading skin tests will remain in the final version of the Centers for Disease Control and Prevention (CDC) guidelines, says Ken Castro, MD, assistant surgeon general of the Public Health Service and director of the Division of Tuberculosis Elimination.

"The [screening] tool is only as good as our ability to administer and read it," he says. "If we're going to rely on this tool, we're going to need to be trained on how to do it well."

Some common problems occur with the test, Castro adds. Sometimes, the skin test is administered intramuscularly instead of intradermally. Some readers can't distinguish between redness and induration, he says, and they may have never seen a positive TB skin test.

CDC recommends recruiting volunteers with known positive skin tests so a trainee can practice reading a positive result. Annual retraining of those administering and reading skin tests also is recommended.

According to the draft guidelines, initial training for a skin test placer involves:

  • Three hours of introductory lecture and demonstration by an expert TST (tuberculin skin test) placer or trainer.
  • Nine hours of supervised practical work using procedural checklists and coached by the expert TST trainer.
  • Administering 10 or more skin tests on volunteers, using injectable saline, and producing 10 or more wheals that measure 6 mm to 10 mm.

The initial training for a TST reader involves these steps:

  • Six hours of introductory lecture and demonstration by an expert TST reader.
  • Four sessions (16 hours total) of supervised practical work using procedural checklists (observed and coached by an expert TST reader).
  • Performing 80 or more blinded independent duplicate readings. TST trainers should attempt to organize the sessions so that at least 50% of the TST results read have a result of greater than 0 mm, according to the expert TST reader.
  • On the last day of TST training, performing 30 or more blinded, independent duplicate readings (out of the total 80 readings). TST trainers should attempt to ensure that at least 25% of those tested have a TST result of greater than 0 mm, according to the expert TST readers.
  • Missing no more than two items on the procedural observation checklist (recommended by CDC) for three random observations by an expert TST reader.
  • Performing all procedures on the checklist correctly during the final observation.