Predictive value for progression to tuberculosis by IGRA and TST in immigrant contacts

Area of Science:

• Infectious Diseases
• Immunology
• Public Health

Background:

• Tuberculosis (TB) remains a global health concern, particularly in immigrant populations.
• Accurate diagnostic tools are crucial for identifying individuals at high risk of TB progression.
• Interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) are used to detect latent TB infection.

Purpose of the Study:

• To compare the positive predictive value (PPV) of two IGRAs (QuantiFERON-TB Gold In-tube and T-SPOT.TB) and the TST for predicting progression to active TB disease.
• To evaluate the effectiveness of these diagnostic tests in immigrant close contacts of infectious TB patients.

Main Methods:

• A cohort of immigrant close contacts (aged >=16 years) with TST results >=5 mm were followed for 2 years.
• Results from QuantiFERON-TB Gold In-tube (QFT-GIT) and T-SPOT.TB were analyzed alongside TST results.
• The incidence of active TB disease was recorded, and PPVs were calculated for different test thresholds.

Main Results:

• Nine out of 339 contacts developed active TB.
• The PPV for progression to TB was comparable across tests: TST (>=10 mm) 3.1%, TST (>=15 mm) 3.8%, QFT-GIT 2.8%, and T-SPOT.TB 3.3%.
• Sensitivities varied: TST 100%, T-SPOT.TB 75%, QFT-GIT 63%, and TST 88% for >=15mm.

Conclusions:

• QFT-GIT, T-SPOT.TB, and TST demonstrate comparable predictive values for TB progression in immigrant close contacts.
• These widely used diagnostic tests are valuable tools for risk stratification in this population.
• Further research may explore optimizing test interpretation and management strategies based on these findings.