Classification of the positive tuberculin skin test (PPD) reaction [18].

Table 2: Classification of the positive tuberculin skin test (PPD) reaction [18].

Induration ≥ 5 mm	Induration ≥ 10 mm	Induration ≥ 15 mm
- A recent contact of a person with active TB disease - A person with fibrotic changes on chest radiograph consistent with prior TB - A patient with an organ transplant - Immunosuppressed patient (e.g., prednisone > 15 mg/day of for one month or longer, taking TNF-a antagonists) - HIV-patient	- Elderly patients - Migrants or expatriate workers from high-prevalence countries (< 5 years) - Exposed infants, children, and adolescents to high-risk adults - IV drug user - Healthcare workers personnel - Detrimental Lifestyle (e.g., crowded accommodation, illicit drug use or alcoholism) - Imprisonment - Related to underlying co-morbidities illnesses - Patients in residential care	- No known risk factors for TB

Induration ≥ 5 mm

Induration ≥ 10 mm

Induration ≥ 15 mm

- A recent contact of a person with active TB disease

- A person with fibrotic changes on chest radiograph consistent with prior TB

- A patient with an organ transplant

- Immunosuppressed patient (e.g., prednisone > 15 mg/day of for one month or longer, taking TNF-a antagonists)

- HIV-patient

- Elderly patients

- Migrants or expatriate workers from high-prevalence countries (< 5 years)

- Exposed infants, children, and adolescents to high-risk adults

- IV drug user

- Healthcare workers personnel

- Detrimental Lifestyle (e.g., crowded accommodation, illicit drug use or alcoholism)

- Imprisonment

- Related to underlying co-morbidities illnesses

- Patients in residential care

- No known risk factors for TB