Table 2. Interpretation of positive result of tuberculin test.

PT ≥5 mm considered positive

Patients infected with HIV.

Close contact with persons who have pulmonary or laryngeal TB.

Children <5 years not previously vaccinated with BCG and who come from countries with a high incidence.

Radiological evidence of previously cured TB, in patients who were did not receive therapy of any recognised efficacy.

Persons receiving organ transplants.

persons with depressed immune systems for other reasons: e.g. receiving doses equivalent to ≥15 mg/day of prednisone for a month or more, or persons starting biological therapy.

Persons with advanced kidney disease.

PT ≥10 mm considered positive

Immigrants from areas with high prevalence of TB in last five years.

Intravenous drug users.

Residents and employees in places where high risk situations take place: medical facilities with exposure to TB, microbiology lab staff, prisons, hostels, refuges for the homeless, geriatric residences, drug dependency centres, volunteers and military personnel in areas with high levels of endemic tuberculosis.

Persons with risk factors for TB different from HIV infection.

Patients with clinical conditions such as: silicosis, diabetes, chronic kidney failure undergoing renal replacement therapy, blood diseases (leukaemia and lymphomas), other malignant tumours (carcinoma of head, neck or lung), weight loss of over 10% under ideal weight, gastrectomy, jejunoileal bypass, celiac disease.

Children <5 years (except for children from countries with a high incidence and not vaccinated with BCG).

Children and adolescents exposed to adults who belong to groups with a high risk of progression of TB.

PT ≥15 mm considered positive

Vaccinated persons, unless they already meet one of the above criteria.

Persons without known risk factors and under risk of infection (administrative screening).

Note. BCG: bacillus Calmette-Guérin; TT: tuberculin test; TB: tuberculosis; HIV: human immunodeficiency virus.