Risk Assessment of Tuberculosis in Contacts by IFN-γ Release Assays. A Tuberculosis Network European Trials Group...

Area of Science:

• Infectious Diseases
• Public Health
• Immunology

Background:

• Latent tuberculosis infection (LTBI) is defined by positive Interferon-Gamma Release Assay (IGRA) results without active disease.
• Few studies have assessed IGRA's predictive value for tuberculosis development in recent contacts in low-incidence countries.

Purpose of the Study:

• To evaluate IGRA results in predicting tuberculosis progression.
• To analyze the impact of preventive chemotherapy on tuberculosis rates among recent contacts.

Main Methods:

• Prospective collection and analysis of contact investigation data from 26 centers across 10 European countries.
• Utilized QuantiFERON-TB Gold In-Tube (QFT) and T-SPOT.TB (TSPOT) assays for latent infection testing.
• Monitored tuberculosis incidence among contacts over a cumulative follow-up period.

Main Results:

• Tuberculosis incidence was significantly lower in IGRA-positive contacts receiving preventive chemotherapy (0.2/100 patient-years for QFT, 0/100 patient-years for TSPOT) compared to those untreated (1.2/100 patient-years for QFT, 0.8/100 patient-years for TSPOT).
• Preventive chemotherapy required treating 37-38 individuals to prevent one case of tuberculosis.
• IGRA assays demonstrated high negative predictive values (99.7-99.9%) but low positive predictive values (0.7-1.9%) for tuberculosis development.

Conclusions:

• Tuberculosis development is infrequent among recent contacts.
• Preventive chemotherapy is effective in reducing tuberculosis risk for IGRA-positive contacts.
• While IGRAs have high negative predictive value, their ability to predict active tuberculosis development is limited.