QuantiFERON-TB Gold (QFT) and Tuberculin Skin Test (TST): Introduction, Differences, and Keynotes

Introduction of QFT) and TST

Interferon-Gamma Release Assays (IGRAs) are a newer blood test for tuberculosis that detects TB infection by measuring the release of interferon-gamma (IFN-g) from patient T cells after stimulation of a whole blood sample with highly specific TB antigens. QuantiFERON-TB Gold (QFT) is a highly sensitive and specific assay than the conventional tuberculin skin test (TST) in which interferon-gamma is tested.

TST is also familiar with the tuberculin tests or tuberculosis skin tests or Mendel–Mantoux test or tuberculin sensitivity tests or purified protein derivative (PPD) tests. It is a tool for screening for tuberculosis. The standard recommended tuberculin test is the Mantoux test and it determines if someone has developed an immune response to the bacterium that causes tuberculosis i.e. M. tuberculosis. PPD used in this test is the extract the components of the organism from TB cultures. This response can occur if someone currently has tuberculosis, if they were exposed to it in the past, or if they received the BCG vaccine against tuberculosis.

QuantiFERON-TB Gold (QFT) and Tuberculin Skin Test (TST): Introduction, Differences, and Keynotes
QuantiFERON-TB Gold and Tuberculin Skin Test (TST) Information

Differences between QuantiFERON-TB Gold (QFT) and Tuberculin Skin Test (TST)

The differences between QFT and TST are as follows-

FeaturesQuantiFERON-TB GoldTuberculin Skin Test
Short-form the testQFTTST
Nature of the testInterferon-gamma Release AssaysTuberculin sensitivity tests
SensitivityLow sensitiveHighly sensitive
Specificity Low (59% of BCG-vaccinated
High (>99%)
False positivesDue to cross-reaction with
the BCG vaccine and other environmental
Unaffected by the BCG vaccine and most non-TB mycobacteria, reducing unnecessary antimicrobial
Patient Follow up Single-visit testingDouble visit testing
Origin of testLatestcentury-old skin test
Table: QuantiFERON-TB Gold (QFT) Vs Tuberculin Skin Test (TST)

Keynotes on QFT and TST

  • Estimates indicate that one-third of the world’s population has latent tuberculosis (TB), and around 1.3 million people worldwide die of TB each year.
  • TST challenges are high program costs from second visits, unnecessary x-rays, and treatment
  • QuantiFERON-TB Gold is a simple, cost-effective solution for tuberculosis screening.
  • 3 ml of whole blood is required for QFT and it is ELISA based assay.

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