Classification of Tuberculin Reaction
The results of this test must be interpreted carefully. The person's medical risk factors determine at which increment (5 mm, 10 mm, or 15 mm) of induration the result is considered positive. A positive result indicates TB exposure.
- 5 mm or more is positive in
- An HIV-positive person
- Persons with recent contacts with a TB patient
- Persons with nodular or fibrotic changes on chest X-ray consistent with old healed TB
- Patients with organ transplants, and other immunosuppressed patients
- 10 mm or more is positive in
- Recent arrivals (less than five years) from high-prevalence countries
- Injection drug users
- Residents and employees of high-risk congregate settings (e.g., prisons, nursing homes, hospitals, homeless shelters, etc.)
- Mycobacteriology lab personnel
- Persons with clinical conditions that place them at high risk (e.g., diabetes, prolonged corticosteroid therapy, leukemia, end-stage renal disease, chronic malabsorption syndromes, low body weight, etc.)
- Children less than four years of age, or children and adolescents exposed to adults in high-risk categories
- 15 mm or more is positive in
- Persons with no known risk factors for TB
(Note: Targeted skin testing programs should only be conducted among high-risk groups)
A tuberculin test conversion is defined as an increase of 10 mm or more within a two-year period, regardless of age.
Read more about this topic: Mantoux Test
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