Hello and welcome to HCM.
Thank you for your query.
A positive Mantoux test
(skin test for TB) is:
1. If above 5 mm in individuals:
-Recent contact with TB infected person
-With x-ray changes or old TB
2. If above 10 mm:
-Injection drug users
-Travel from high-prevalence countries (less than 5 years)
-Employed or residing in areas with high-prevalence
-Other risk factors present (diabetes
, immunosuppressed, terminal stage diseases, malnutrition
-Children less than 4 years of ago
3. More than 15 mm:
-No previous risk factors of TB
If positive, you will also have to rule out a false-positive result.
I hope I have succeeded in answering your questions, you could write back to me anytime for further clarifications.