Identification of Recent Tuberculosis Exposure Using QuantiFERON-TB Gold Plus, a Multicenter Study.

Area of Science:

• Infectious Diseases
• Immunology
• Public Health

Background:

• Contact tuberculosis tracing is crucial for identifying recently infected individuals eligible for preventive treatment.
• Current diagnostic tools lack the ability to definitively distinguish recent TB infection from remote exposure.
• The QuantiFERON-TB Gold Plus (QFT-Plus) assay's TB2-TB1 difference has been proposed as a surrogate marker for recent TB infection.

Purpose of the Study:

• To evaluate if the difference between antigen tubes (TB2-TB1) in the QFT-Plus assay can identify recent tuberculosis (TB) exposure.
• To assess the utility of the TB2-TB1 interferon gamma (IFN-γ) response difference as a proxy marker for recent TB infection.

Main Methods:

• Analyzed IFN-γ responses and TB2-TB1 differences in 686 adults with positive QFT-Plus results.
• Compared QFT-Plus results among groups with high (TB contacts), low (immune-mediated inflammatory diseases [IMID]), and indeterminate (asylum seekers/people from abroad [ASPFA]) risks of recent TB exposure.
• Investigated TB2-TB1 differences within TB contact subgroups (close, frequent, sporadic).

Main Results:

• No significant association was found between a TB2-TB1 difference >0.6 IU·ml⁻¹ and increased risk of recent TB exposure across different risk groups (contacts, IMID, ASPFA).
• The prevalence of TB2>TB1 results did not differ significantly among the contact, IMID, and ASPFA groups (13.6%, 10.9%, 11.2% respectively).
• TB2-TB1 differences did not effectively classify individuals based on recent TB exposure risk within contact subgroups.

Conclusions:

• The TB2-TB1 difference in the QFT-Plus assay is not a reliable marker for identifying recent tuberculosis infection.
• The QFT-Plus assay cannot differentiate between recent and remotely acquired TB infections.
• The QFT-Plus assay should not be used for distinguishing recent TB infection in contact tracing.