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Interferon Gamma Release Assay Results and Testing Trends Among Patients Younger Than 2 Years Old at Two US Health
Mary E Tabatneck1, Wei He2, Gabriella S Lamb3
1From the Department of Pediatrics, Boston Children's Hospital, Boston, Massachusetts.
Insights
Interferon-gamma release assays (IGRAs) show high validity in children under two years old for diagnosing tuberculosis (TB). While generally reliable, results in immunocompromised children require careful clinical interpretation.
Area of Science:
- Pediatric Infectious Diseases
- Diagnostic Immunology
- Mycobacterial Infections
Background:
- Interferon-gamma release assays (IGRAs) are approved for diagnosing Mycobacterium tuberculosis (TB) infection in children aged 2 years and older.
- Tuberculin skin tests (TSTs) remain the recommended diagnostic method for TB infection in children younger than 2 years, due to limited data and concerns about uninterpretable results with IGRAs.
Purpose of the Study:
- To evaluate the utility and validity of IGRA testing in pediatric patients under 2 years of age.
- To assess the concordance between IGRA and TST results in this age group.
- To analyze trends in IGRA utilization over time for young children.
Main Methods:
- A retrospective cohort study was conducted analyzing IGRA results from patients under 2 years old across two major Boston healthcare systems.
- The primary outcome measured was the proportion of valid versus invalid/indeterminate IGRA results.
- Secondary outcomes included comparing IGRA results with paired TSTs and examining the increasing use of IGRAs.
Main Results:
- Out of 321 analyzed IGRA results, 96% were valid, with only 4% being invalid/indeterminate.
- Immunocompromised patients had a significantly higher rate of invalid/indeterminate IGRA results (27%) compared to immunocompetent patients (1%).
- Paired IGRA and TST results showed a 64% concordance rate, with discrepancies often noted in bacille Calmette-Guérin-vaccinated individuals. IGRA use increased significantly over the study period.
Conclusions:
- The high proportion of valid IGRA results in young children, coupled with TST challenges, supports considering IGRAs for this age group in specific clinical situations.
- Careful interpretation of IGRA results, especially in immunocompromised children, is essential within the broader clinical context.
Background:
Interferon-gamma release assays (IGRAs) are approved for children ≥2 years old to aid in diagnosis of Mycobacterium tuberculosis (TB) infection and disease. Tuberculin skin tests (TSTs) continue to be the recommended method for diagnosis of TB infection in children <2 years, in part due to limited data and concern for high rates of uninterpretable results.
Methods:
We performed a retrospective cohort study of IGRA use in patients <2 years old in 2 large Boston healthcare systems. The primary outcome was the proportion of valid versus invalid/indeterminate IGRA results. Secondary outcomes included concordance of IGRAs with paired TSTs and trends in IGRA usage over time.
Results:
A total of 321 IGRA results were analyzed; 308 tests (96%) were valid and 13 (4%) were invalid/indeterminate. Thirty-seven IGRAs were obtained in immunocompromised patients; the proportion of invalid/indeterminate results was significantly higher among immunocompromised (27%) compared with immunocompetent (1%) patients ( P < 0.001). Paired IGRAs and TSTs had a concordance rate of 64%, with most discordant results in bacille Calmette-Guérin-vaccinated patients. The proportion of total TB tests that were IGRAs increased over the study period (Pearson correlation coefficient 0.85, P < 0.001).
Conclusions:
The high proportion of valid IGRA test results in patients <2 years of age in a low TB prevalence setting in combination with the known logistical and interpretation challenges associated with TSTs support the adoption of IGRAs for this age group in certain clinical scenarios. Interpretation of IGRAs, particularly in immunocompromised patients, should involve consideration of the broader clinical context.
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