Hi, Thanks for writing in. The magnitude of skin reaction is interpreted. Induration of 5 mm is considered positive in: Human immunodeficiency virus (HIV)-infected persons Recent contacts of TB case patients Persons with fibrotic changes on chest radiograph consistent with prior TB Patients with organ transplants and other immunosuppressed patients (e.g., receiving the equivalent of 15 mg/d of prednisone for 1 month or more) Induration of 10 mm is considered positive in: Recent immigrants (i.e., within the last 5 years) from countries with a high prevalence of TB Injection drug users Residents and employees of the following high-risk congregate settings: - prisons and jails - nursing homes and other long-term facilities for the elderly - hospitals and other health care facilities - residential facilities for patients with acquired immunodeficiency syndrome (AIDS) - homeless shelters Mycobacteriology laboratory personnel Persons with the following clinical conditions that place them at high risk: - silicosis - diabetes mellitus - chronic renal failure - some hematologic disorders (e.g., leukemias and lymphomas) - other specific malignancies (e.g., carcinoma of the head, neck, or lung) - weight loss of 10% of ideal body weight - gastrectomy - jejunoileal bypass Children 5 years of age Infants, children, and adolescents exposed to adults at high risk for developing active TB Induration of 15 mm is considered positive in: Persons with no known risk factors for TB