According to the Tuberculosis Control Program guidance, a positive result on the tuberculin skin test (TST) is recorded for induration of how many mm or more?

A positive result on the tuberculin skin test (TST) is recorded for induration of 10 mm or more. This threshold is significant because it indicates a higher likelihood of tuberculosis infection, especially in individuals with varying risk factors. The TST measures the immune response to a protein derived from the tuberculosis bacteria; if a person has been exposed, their body will react with swelling at the test site.

The 10 mm measurement is particularly important in assessing populations who may be at increased risk for tuberculosis, including those who have had recent contact with infectious TB cases, individuals with weakened immune systems, or those with certain medical conditions.

The lower thresholds, such as 5 and 15 mm, are used as well, but they apply to specific groups with unique risk factors. For instance, a 5 mm induration may be considered positive for HIV-positive individuals or others with severe immunosuppression, while 15 mm is regarded as a positive response for individuals with no known risk factors. However, for a general population without these specific conditions, 10 mm serves as the standard cut-off for positivity in the TST.