[Critical approach to the use of blood tests measuring gamma-interferon when suspecting active tuberculosis: clinical

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Jean-Paul Janssens1

  • 1Centre antituberculeux, HUG, 1211 Geneve 14. Jean-Paul.Janssens@hcuge.ch

Revue Medicale Suisse
|March 9, 2007
PubMed

Insights

Interferon-gamma release assays (IGRA) offer high specificity for detecting Mycobacterium tuberculosis infection, outperforming the tuberculin skin test (TST) in certain populations. However, IGRA cannot differentiate between latent tuberculosis infection (LTBI) and active disease.

Area of Science:

  • Immunology
  • Infectious Diseases
  • Mycobacteriology

Background:

  • The tuberculin skin test (TST) is a traditional method for diagnosing tuberculosis (TB) infection.
  • TST can yield false positive results due to BCG vaccination or non-tuberculous mycobacteria.
  • Accurate diagnosis is crucial for effective treatment of latent tuberculosis infection (LTBI).

Observation:

  • Interferon-gamma release assays (IGRA) measure immune response to Mycobacterium tuberculosis antigens.
  • Peripheral lymphocytes are stimulated with specific antigens to assess gamma-interferon production.
  • IGRA demonstrates high specificity, reducing false positives common with TST.

Findings:

  • IGRA exhibits superior sensitivity compared to TST in immunocompromised and elderly individuals.
  • Sensitivity of IGRA is likely higher than TST in immunocompetent individuals as well.
  • IGRA cannot distinguish between latent TB infection (LTBI) and active TB disease.
  • IGRA sensitivity is insufficient to rule out active TB, particularly in immunocompromised patients.

Implications:

  • IGRA is valuable for LTBI detection in screening, contact tracing, and immunocompromised individuals.
  • High specificity of IGRA aids in precise treatment targeting for LTBI.
  • Limitations in differentiating active TB necessitate further diagnostic evaluation when using IGRA.

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