What induration size indicates a positive Mantoux test in high-risk individuals?

What induration size indicates a positive Mantoux test in high-risk individuals?

• A. Induration greater than 5 mm
• B. Induration greater than 15 mm
• C. Induration greater than 20 mm
• D. Induration greater than 10 mm

Answer: (D)

The test uses the size of the induration to gauge the likelihood of TB infection, and the threshold is lower for those at higher risk. In high-risk individuals, an induration larger than 10 millimeters is considered a positive reaction, meaning TB infection is possible and further evaluation is needed. The measurement refers to the raised, firm area (induration) after 48–72 hours, not just redness. Smaller thresholds like greater than 5 mm are used for the highest-risk groups (e.g., HIV), while greater than 15 mm is used for those with fewer risk factors; 20 mm is not a standard cutoff in typical guidelines.

The test uses the size of the induration to gauge the likelihood of TB infection, and the threshold is lower for those at higher risk. In high-risk individuals, an induration larger than 10 millimeters is considered a positive reaction, meaning TB infection is possible and further evaluation is needed. The measurement refers to the raised, firm area (induration) after 48–72 hours, not just redness. Smaller thresholds like greater than 5 mm are used for the highest-risk groups (e.g., HIV), while greater than 15 mm is used for those with fewer risk factors; 20 mm is not a standard cutoff in typical guidelines.