From the Guidelines
The Mantoux test is a crucial screening tool for tuberculosis in children, particularly those under 5 years old, as it helps identify latent TB infection and prevent progression to active disease, as emphasized by the 2009 study 1. The test involves injecting 0.1 mL of purified protein derivative (PPD) intradermally on the volar aspect of the forearm, creating a small wheal. The test should be read 48-72 hours after administration by measuring the diameter of induration (hardened area) in millimeters, not just redness. Some key points to consider when interpreting the results of the Mantoux test include:
- Interpretation varies by risk factors: ≥5 mm is positive in immunocompromised children or those with known TB contacts; ≥10 mm is positive in children under 4 years or with specific risk factors; and ≥15 mm is positive in children without risk factors.
- False negatives can occur in immunocompromised patients, recent TB infection, overwhelming TB disease, recent live virus vaccination, or improper technique.
- False positives may result from non-tuberculous mycobacterial infection or BCG vaccination, though BCG's effect typically wanes after 5-10 years. As highlighted by the 2005 study 1, children aged <5 years who have been identified as contacts of persons with infectious TB should receive a clinical evaluation, including a tuberculin skin test and chest radiograph, to rule out active TB. Additionally, the 2005 study 1 recommends that asymptomatic children with a positive PPD-tuberculin skin test and an abnormal chest radiograph should receive combination chemotherapy, usually with INH, RIF, and PZA as initial therapy. It is also important to note that, as stated in the 2003 study 1, the optimal treatment of pulmonary tuberculosis in children and adolescents with HIV infection is unknown, but initial therapy should always include at least three drugs (INH and RIF, plus PZA for the first 2 months), and the total duration of therapy should be at least 9 months. In summary, the Mantoux test is a vital tool in pediatric TB screening, and its results should be interpreted in the context of the child's risk factors and medical history, as emphasized by the studies 1.
From the Research
Significance of the Mantoux Test in Pediatrics
The Mantoux test, also known as the Tuberculin Skin Test, is a crucial diagnostic tool in pediatrics for detecting tuberculosis (TB) infection. The test involves injecting a small amount of purified protein derivative (PPD) into the skin, and the reaction is measured after 48-72 hours.
Interpretation and Variability
- The test results are interpreted based on the size of induration, which can vary depending on the reader and the time of reading 2.
- A study found significant interobserver variability in reading the Mantoux test, with a tendency to under-read around the cutoff point of 10-14 mm 2.
- The use of 5 TU PPD at 48 hours by a trained physician can aid in early and more reliable diagnosis of TB 2.
Application and Recommendations
- The American Academy of Pediatrics recommends annual screening with the Mantoux test for high-risk children, although a study found that children exposed to poor and medically indigent city dwellers may not represent a high-risk group 3.
- Routine screening with the Mantoux test is important in persons at high risk of infection or progression to active disease, and test results are interpreted on the basis of each patient's risk factors 4.
- The Mantoux test is also used to determine immunity to tuberculosis in humans, and positive reactions develop in individuals previously exposed to Mycobacterium tuberculosis or immunized with the Bacillus of Calmette and Guérin (BCG) vaccine 5.
Clinical Applications and Associations
- The Mantoux test is associated with hypersensitivity reactions to Mycobacterium tuberculosis, including papulonecrotic tuberculid, lichen scrofulosorum, erythema induratum of Bazin, and phlebitic tuberculid 6.
- A strong positive Mantoux test can indicate the presence of associated tuberculosis, and the test is used to diagnose and monitor treatment of TB 6.
- The Mantoux test can also be used as a model for a secondary immune response in humans, representing a cutaneous T cell mediated memory recall immune response 5.