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Predictive value of recent QuantiFERON conversion for tuberculosis disease in adolescents
Shingai Machingaidze1, Suzanne Verver, Humphrey Mulenga
1South African Tuberculosis Vaccine Initiative (SATVI), Institute of Infectious Disease and Molecular Medicine (II), University of Cape Town, Cape Town, South Africa.
American Journal of Respiratory and Critical Care Medicine
|September 8, 2012
Summary
Recent interferon-gamma release assay (IGRA) conversion, specifically QuantiFERON-TB Gold In-Tube (QFT), indicates a significantly higher risk of developing tuberculosis (TB) disease. This finding highlights the importance of monitoring IGRA converters in high-burden populations.
Area of Science:
- Infectious Disease Epidemiology
- Mycobacterium tuberculosis Diagnostics
- Public Health Surveillance
Background:
- Serial testing with Interferon-Gamma Release Assays (IGRA) can show conversions and reversions, similar to the Tuberculin Skin Test (TST).
- Recent TST conversion is a known risk factor for tuberculosis (TB) disease progression.
- The risk of TB disease following recent IGRA conversion remains largely uncharacterized.
Purpose of the Study:
- To evaluate and compare the incidence rate of TB disease in adolescents who recently converted their QuantiFERON-TB Gold In-Tube (QFT) test results versus those who remained QFT negative.
- To quantify the risk associated with recent IGRA conversion in a high-TB burden setting.
Main Methods:
- A cohort study design was employed, identifying adolescents with QFT conversion (n=534) and a control group of adolescents with persistently negative QFT results (n=629).
- Participants were followed over a 2-year period to ascertain TB disease incidence.
- Statistical analysis compared TB disease rates between the QFT converter and non-converter groups.
Main Results:
- The TB incidence rate among QFT converters was 1.46 per 100 person-years, with a cumulative incidence of 2.8%.
- QFT non-converters exhibited a significantly lower TB incidence rate of 0.17 per 100 person-years and a cumulative incidence of 0.32%.
- The incidence rate ratio for TB disease was 8.54 (all cases) and 9.1 (protocol-defined TB) for QFT converters compared to non-converters.
Conclusions:
- Recent QFT conversion is associated with a substantially increased risk, approximately eightfold, of progressing to active TB disease within two years.
- These findings underscore the clinical significance of IGRA conversion as an indicator of recent TB infection and elevated disease risk.
- The study emphasizes the need for targeted monitoring and potential interventions for individuals with recent IGRA conversions in high-incidence populations.
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