What is the sensitivity of the Quantiferon (Interferon-Gamma Release Assay) test in detecting active tuberculosis?

Sensitivity of QuantiFERON-TB Gold in Active Tuberculosis

The QuantiFERON-TB Gold (QFT) test has a sensitivity of approximately 81-83% for detecting active tuberculosis in patients with culture-confirmed disease, which is lower than the T-SPOT.TB test (91%) but comparable to tuberculin skin test (TST) in many studies. 1

Sensitivity Rates Across Different IGRA Tests

QuantiFERON-TB Gold In-Tube (QFT-GIT)

• Pooled sensitivity: 81% in culture-confirmed TB cases 1
• Range: 70-83% depending on study methodology 1
• Sensitivity in specific populations:
  • 80% in a 2013 study against culture-positive TB 2
  • 81% in a 2008 study of suspected active TB 3

T-SPOT.TB Test

• Pooled sensitivity: 91% in culture-confirmed TB cases 1
• Generally higher sensitivity than QFT-GIT in head-to-head comparisons 1

Newest Generation (QFT-Plus)

• Improved sensitivity: 98.9% in a 2018 Japanese study 4
• Comparable to QFT-GIT (97.9%) and T-SPOT (96.9%) in the same study 4

Comparison with Tuberculin Skin Test (TST)

• In culture-confirmed TB:

  • QFT-GIT: 83% sensitivity
  • TST: 89% sensitivity 1

• Age-stratified comparison:

  • TST sensitivity decreases significantly with age (>80 years: 33%)
  • QFT maintains higher sensitivity in elderly (>80 years: 75%) 5
  • QFT significantly outperforms TST in patients over 50 years 5

• In a 2013 study:

  • QFT-G: 80% sensitivity
  • TST: only 28% sensitivity 2

Factors Affecting Sensitivity

Age

• QFT maintains relatively stable sensitivity across adult age groups (>80% for ages 10-69) 5
• Slightly reduced in elderly (79% in 70-79 years, 75% in >80 years) 5
• Lower sensitivity in children under 9 years 5

Immunosuppression

• Indeterminate results increase with age and underlying diseases 5
• Diabetes mellitus (especially uncontrolled) may cause false negatives 4
• HIV and other immunosuppressive conditions can reduce sensitivity 6

Clinical Implications

• QFT can be a useful adjunct to diagnosis in patients with clinical and radiological findings compatible with TB 2

• Benefits over TST:

  • Unaffected by prior BCG vaccination
  • Less cross-reactivity with non-tuberculous mycobacteria 2
  • Better performance in elderly populations 5

• Limitations:

  • Cannot differentiate between active and latent TB infection 6
  • Sensitivity not high enough to rule out active TB when negative
  • Performance varies by population characteristics and immune status 6

Pitfalls and Caveats

1. A negative QFT result does not exclude active TB due to the ~20% false-negative rate
2. Indeterminate results are more common in immunocompromised patients
3. Sensitivity is lower in children under 5 years, warranting caution in this age group 1
4. Uncontrolled diabetes may lead to false-negative results 4
5. Test performance can vary by ethnic group and BCG vaccination status 6

The CDC guidelines emphasize that IGRAs and TST should be considered imperfect tests, and negative results from either test do not definitively rule out M. tuberculosis infection in persons with symptoms or signs suggestive of TB disease 1.