SEARCHED TERM
Tuberculin skin test (TST) conversion
DEFINITION
A change from a negative test result to a positive test result. The size of the change in the induration needs to be considered, as conversion varies based on the baseline testing results and whether the person has a known exposure to a person with tuberculosis. A TST conversion typically is interpreted as presumptive evidence of new M. tuberculosis infection and poses an increased risk for progression to tuberculosis.
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SOURCE DEFINITION
In programs using the TST method of screening, a change from a negative test result to a positive test result. The size of the change in mm induration needed to be considered a conversion varies based on the baseline testing results and whether the person has a known exposure to a TB patient. A TST conversion typically is interpreted as presumptive evidence of new M. tuberculosis infection and poses an increased risk for progression to TB disease.
OTHER DEFINITIONS
Test response in an individual previously classified as a non-reactor
Person who is assumed to have become tuberculin positive recently as a result of natural infection. This may be a previously tuberculin negative person, or a person who has previously been vaccinated against TB and who now has a definitely enhanced tuberculin reaction as a result of re-infection
See Conversion
Increase of >10 mm of induration within a 2-yr period, regardless of age
Change from negative to positive with an increase of ≥10 mm in induration within 2 years
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