CRITERIA FOR INTERPRETING A MANTOUX TB TEST TO BE POSITIVE

Induration of >5mm is considered positive in:

  • Human Immunodeviciency Virus (HIV)-infected persons
  • Recent contacts of TB case patients
  • Persons with fibrotic changes on chest radiograph consistant with prior TB.
  • Patients with organ transplants and other immunosuppressed patients (e.g., receiving the equivalent of > 15mg/d of prednisone for 1 month or more)
  • Patients taking medications associated with tumor necrosis or arthritis

Induration of >10mm 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 care facilities for the elderly
  •    Hospitals and other healthcare 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 > 15mm is considered positive in

  • Persons with no known risk factors for TB

NOTE: The Mantoux test should be read 48 to 72 hours after the injection, and the diameter of induration (not erythema) should be measured transversely to the long axis of the forearm and recorded in millimeters.