According to CDC guidelines, what induration size is considered positive in all other cases?

According to CDC guidelines, what induration size is considered positive in all other cases?

• A. 5 mm
• B. 10 mm
• C. 15 mm
• D. 20 mm

Answer: (C)

Interpreting the tuberculin skin test depends on risk factors. For people with no known TB risk factors, a positive result is an induration of fifteen millimeters or more. This threshold helps keep false positives low in low-risk populations while still catching true infections when risk is present. In higher-risk groups, smaller indurations are considered positive (for example, five millimeters for HIV or recent TB contact; ten millimeters for other risk factors). A larger induration, such as twenty millimeters, would also be positive, but fifteen millimeters is the standard universal cutoff for those without risk factors. Remember, the reading is the palpable induration measured in millimeters after 48–72 hours, not the redness.

Interpreting the tuberculin skin test depends on risk factors. For people with no known TB risk factors, a positive result is an induration of fifteen millimeters or more. This threshold helps keep false positives low in low-risk populations while still catching true infections when risk is present. In higher-risk groups, smaller indurations are considered positive (for example, five millimeters for HIV or recent TB contact; ten millimeters for other risk factors). A larger induration, such as twenty millimeters, would also be positive, but fifteen millimeters is the standard universal cutoff for those without risk factors. Remember, the reading is the palpable induration measured in millimeters after 48–72 hours, not the redness.