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Tuberculin skin testing and T-SPOT.TB in internationally adopted children
Kevin B Spicer1, Joanne Turner, Shu-Hua Wang
1From the *College of Medicine, The Ohio State University, Columbus, OH and †Section of Infectious Diseases, Nationwide Children's Hospital, Columbus, OH.
Insights
Tuberculin skin test (TST) may overestimate latent tuberculosis infection in international adoptees. T-SPOT.TB assay showed fewer positive results, especially in children under one year old, suggesting it may be more reliable for diagnosing TB infection.
Area of Science:
- Pediatrics
- Infectious Diseases
- Diagnostic Immunology
Background:
- Diagnosing latent tuberculosis infection (LTBI) in children is challenging due to lack of a standard diagnostic test.
- Previous Bacillus Calmette-Guérin (BCG) vaccination and environmental mycobacteria exposure can affect test results.
- The effectiveness of interferon-gamma release assays (IGRAs) in young children requires further demonstration.
Purpose of the Study:
- To evaluate the agreement between the tuberculin skin test (TST) and the T-SPOT.TB assay in children.
- To identify factors associated with positive TST and T-SPOT.TB results.
- To assess the impact of age on the performance of these tests in international adoptees.
Main Methods:
- A prospective cohort study was conducted with 109 children (4 months to 16 years) from an international adoption clinic.
- Children were adopted from 14 countries, with the majority from China, Russia, and Ethiopia.
- Correspondence between TST and T-SPOT.TB was evaluated, and factors influencing test results, including age, were analyzed.
Main Results:
- The TST was positive in 23.4% of children, while the T-SPOT.TB assay was positive in only 4.6%.
- Overall agreement between TST and T-SPOT.TB was 71% (Kappa = 0.68).
- History of Mycobacterium tuberculosis exposure was linked to positive results for both tests. No children under one year old tested positive on either TST or T-SPOT.TB.
Conclusions:
- The TST may overestimate LTBI in international adoptees compared to the T-SPOT.TB assay.
- Discordant results, with positive TST and negative T-SPOT.TB, were observed.
- Age is a significant factor, with no positive results in children under one year old, suggesting T-SPOT.TB may be more reliable in this age group.
Background:
Diagnosis of latent tuberculosis infection is a problem in children because of lack of a diagnostic standard and potential impact of previous Bacille Calmette-Guérin vaccination and exposure to environmental mycobacteria. Effectiveness and usefulness of interferon-gamma release assays in infants and younger children have yet to be clearly demonstrated.
Methods:
Prospective cohort study including 109 children (4 months to 16 years) seen in an international adoption clinic at Nationwide Children's Hospital, Columbus, OH. Children were adopted from 14 countries, mostly (72.5%) from China, Russia and Ethiopia. Correspondence between tuberculin skin test (TST) and the T-SPOT.TB assay was evaluated. Factors associated with positive results on the TST and T-SPOT.TB were determined, and the impact of age on test performance was specifically addressed.
Results:
TST was positive in 23.4% (25 of 107). T-SPOT.TB was positive in 4.6% (5 of 109). Overall agreement between TST and T-SPOT.TB was 71%, with prevalence-adjusted, bias-adjusted Kappa of 0.68. History of Mycobacterium tuberculosis exposure was associated with positive results on TST (odds ratio: 25.4, 95% confidence interval: 4.8-261.6, exact logistic regression) and T-SPOT.TB (odds ratio: 78.9, 95% confidence interval: 9.7-∞). All 5 children with positive T-SPOT.TB had TST induration ≥15 mm. No patient less than 1 year of age (n = 17) had positive TST or T-SPOT.TB. Positive TST was not associated with Bacille Calmette-Guérin vaccination or scar.
Conclusions:
TST was positive in a significant percentage of international adoptees. T-SPOT.TB was rarely positive and discordant results reflected negative T-SPOT.TB with positive TST. In this population latent tuberculosis infection may be over-estimated by TST. Regardless, in our context at the time of the study, treatment decisions were based upon TST results, not results of the T-SPOT.TB assay. Age was consistently associated with findings on TST and T-SPOT.TB with no positive result on either test for any child <1 year of age.
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