NEW YORK (360Dx) – The US Centers for Disease Control and Prevention has mandated that all US civil surgeons screening immigrants for latent tuberculosis must use an interferon-gamma release assay (IGRA) instead of the decades-old tuberculin skin test (TST).
The CDC is currently revising tuberculosis screening guidelines, referred to as technical instructions, which it provides to the US Department of State and US Citizenship and Immigration Services.
In a notification issued late last week to all US civil surgeons, the CDC said that these new guidelines will go into effect on Oct. 1. At that time, when a test is required for cell-mediated immunity to TB, including for children younger than five, civil surgeons will be required to perform a US Food and Drug Administration-approved IGRA. Currently, they have the option to perform either an IGRA or TST.
The mandate bodes well for Qiagen and Oxford Immunotec, both of which market FDA-approved IGRAs. Oxford Immunotec's T-Spot.TB test received FDA premarket approval in 2008, while Qiagen's QuantiFeron-TB Gold Plus (QFT-Plus) — a fourth-generation version of the test — received FDA approval in June 2017.
IGRAs use tuberculosis peptides to simulate the presence of a specific TB protein, then provide a visual readout immunoassay of whole blood to measure the immune response to these peptides. Qiagen's assay directly measures interferon gamma released from white blood cells, while Oxford Immunotec's test measures the number of IFN-g-producing cells.
Masae Kawamura, Qiagen's senior director for TB medical and scientific affairs, noted in a statement that about 93 percent of TB disease in the US comes from the approximately 13 million-person reservoir of latent TB infections, which primarily occurs through migration from higher-burden countries.
"We look forward to working with the civil surgeons around the US in this transition period since switching from the TB skin test to tests like QFT-Plus can eliminate false-positive results from BCG vaccination used in most countries," Kawamura said. "This makes the QFT-Plus results more accurate and believable to both the physician and the patient."