What is the minimum age for administering the Quantiferon Gold (Interferon-Gamma Release Assay) test?

Minimum Age for QuantiFERON Gold Testing

The minimum recommended age for QuantiFERON Gold (QFT) testing is 5 years, as children under 5 years of age have higher rates of indeterminate results and potentially lower test sensitivity. 1

Age-Related Considerations

Children Under 5 Years

• Higher caution is warranted when using IGRAs (including QFT) in children under 5 years due to:
  • Limited performance data in this age group 1
  • Higher rates of progression from latent TB infection to active disease 1
  • Higher risk of severe forms of TB disease (meningitis, disseminated disease) 1
  • Age-related immunologic differences affecting test performance 1
  • Higher proportion of indeterminate results 1, 2
  • Practical challenges in collecting sufficient blood volume 1

Children 5 Years and Older

• Less caution is required when implementing QFT testing in children ≥5 years 1
• Older children are:
  • Less likely to develop active TB or severe forms of disease 1
  • More similar to adults in immune response 1
  • Logistically easier to test (ability to draw sufficient blood) 1

Performance Characteristics by Age

Under 2 Years

• Suboptimal sensitivity (84.6%) in microbiologically confirmed TB cases 3
• Higher rates of indeterminate results 2
• Lower interferon-gamma production in response to mitogen control 4, 2
• Increasing age is associated with lower rates of indeterminate results (OR 0.948 per month of age) 2

2-4 Years

• Better performance than <2 years but still with limitations
• Sensitivity of 95.0% in microbiologically confirmed TB cases 3
• Still higher risk of discordant TST+/QFT- results compared to older children 3

5 Years and Older

• Performance similar to adults 1, 3
• Sensitivity of 89.1% in microbiologically confirmed TB cases 3
• Lower rates of indeterminate results 1

Technical Considerations

• Blood must be incubated with test antigens within 12 hours of collection 1, 5
• Lymphocyte viability must be maintained 1
• 5-mL blood sample is required, which may be difficult to obtain from young children 1
• Environmental factors like temperature and season may affect test performance 2

Clinical Implications

• For children <5 years, especially <2 years:

  • Consider using both TST and QFT when there is strong clinical suspicion or high-risk TB contact 3
  • Be aware of higher rates of indeterminate results and potential false negatives 1, 2

• For children ≥5 years:

  • QFT can be used with greater confidence, similar to adults 1
  • May be used as a single test in low-risk screening scenarios 3

Pitfalls and Caveats

• Never rely solely on QFT results to exclude TB disease, especially in symptomatic patients 5
• Interpret results in conjunction with clinical, radiographic, and microbiological findings 5
• Be aware that immunocompromised patients have higher risk of false-negative results 5
• Young age and elevated inflammatory markers (ESR) are associated with lower positive control responses 2
• Tobacco smoke exposure may negatively affect test performance 2

While the test can technically be performed in children of any age, the evidence strongly supports using 5 years as the minimum recommended age for routine QFT testing due to more reliable performance and fewer technical challenges.