Re: “Prebiologic Therapy Tuberculosis Screening Experience in a Pediatric Rheumatology Center

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We thank Dr. Marino and colleagues for their report describing their experience using tuberculin skin test (TST) and interferon gamma release assay (IGRA) to detect latent tuberculosis infection (LTBI) among patients attending a pediatric rheumatology center.
Marino et al report that among 120 juvenile idiopathic arthritis patients screened for LTBI using both IGRA and TST, 6 were diagnosed with LTBI; 3 of these patients were TST+/IGRA−, and one was TST−/IGRA+. It is critical to distinguish between the patients described by Dr. Marino and the pool of US-bound immigrant children that we included in our evaluation. The most important difference is that the children in our evaluation were not receiving (or about to receive) tumor necrosis factor-alpha antagonists or other immunosuppressive treatment and so were not at increased risk for progression to active disease. US guidelines for using IGRA to detect Mycobacterium tuberculosis infection emphasize that when the risk for progression and the risk for a poor outcome are increased, testing with both IGRA and TST may be considered to increase sensitivity of LTBI testing.1 We agree that among pediatric rheumatology patients who are being considered for anti–tumor necrosis factor-alpha treatment, it may make sense to use both tests to detect LTBI.
The finding by Marino et al of discordance between IGRA and TST results among 6 patients who were diagnosed with and treated for LTBI adds to the experience that neither TST nor IGRA are perfect tests and that there is no reference standard for evaluating a diagnostic test for LTBI. Despite this, our data suggest that using IGRA at preimmigration screening for BCG-vaccinated children could lead to benefits including a reduction in the burden on immigrant children and domestic US TB control programs by avoiding likely unnecessary chest radiography and LTBI treatment. Because the consequences of missing a case of LTBI in this population are less than that in a population of immunocompromised children, we agree that our conclusion should not necessarily be extended to a population of children receiving immunosuppressive medications. Like Marino et al and Tebruegge et al, we look forward to the development of improved tests for LTBI diagnosis.

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