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Mantoux Tuberculosis Skin Test Facilitator Guide

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Appendix D: Mantoux Tuberculin Skin Test Interpretation Table

Skin test interpretation depends on

  1. the measurement in millimeters (mm) of the induration and
  2. the person’s risk of being infected with TB and/or progression to disease if infected.

The following three cut points should be used to determine whether the skin test reaction is positive. A measurement of 0 mm or anything below the defined cut point for each category is considered negative.

Induration of ≥ 5 mm is considered positive in
Induration of ≥ 10 mm is considered positive in
Induration of ≥ 15 mm is considered positive in
  • Human immunodeficiency virus (HIV)-positive 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 (Receiving the equivalent of ⊃3;15 mg/d of prednisone for 1 month or more. Risk of TB in patients with corticosteroids increases with higher dose and longer duration.)
  • Recent immigrants (i.e., within the last 5 years) from high-prevalence countries
  • 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), and 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 ⊃3;10% of ideal body weight, gastrectomy, and jejunoileal bypass
  • Children < 4 years of age, or infants, children and adolescents exposed to adults at high-risk
  • Persons with no known risk factors for TB

† For persons who are otherwise at low risk for TB and who are tested at the start of employment, a reaction of ≥15 mm is considered positive.

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