First evaluation of QuantiFERON-TB Gold Plus performance in contact screening

Area of Science:

• Immunology
• Infectious Diseases
• Tuberculosis Diagnostics

Background:

• Latent tuberculosis infection (LTBI) identification is key for TB elimination.
• Interferon-gamma release assays (IGRAs) are used to detect LTBI.
• Existing IGRAs primarily stimulate CD4+ T-cells.

Purpose of the Study:

• To evaluate the performance of QuantiFERON-TB Plus (QFT-Plus), a novel IGRA.
• To assess QFT-Plus's ability to detect LTBI in contacts of TB patients.
• To compare QFT-Plus with QuantiFERON-TB Gold In-Tube (QFT-GIT).

Main Methods:

• 119 TB contacts were screened using tuberculin skin test, QFT-Plus, and QFT-GIT.
• QFT-Plus utilizes an additional antigen tube (TB2) to stimulate CD4+ and CD8+ T-cells.
• Interferon-gamma production difference (TB2-TB1) estimated CD8+ T-cell response.

Main Results:

• High agreement (Cohen's κ = 0.8) between QFT-Plus and QFT-GIT.
• 12 subjects showed discordant results (negative QFT-GIT, positive QFT-Plus).
• QFT-Plus demonstrated a stronger association with TB exposure markers (e.g., time with index case) than QFT-GIT.
• CD8+ T-cell response (TB2-TB1 >0.6 IU·mL⁻¹) correlated with proximity to index case and European origin.

Conclusions:

• QFT-Plus shows enhanced association with TB exposure compared to QFT-GIT in adults.
• The CD8+ T-cell response measured by QFT-Plus may identify individuals with recent Mycobacterium tuberculosis exposure.
• QFT-Plus holds potential for improved identification of recent TB infections.