用QuantiFERON-TB Gold test 測IFN r, IL-2可分辨latent TB. active TB


Distinguishing Active from Latent Tuberculosis

A modified QuantiFERON-TB Gold test that simultaneously measures interleukin-2 and interferon-{gamma} levels allowed differentiation between latent infection and active disease.

The recently introduced interferon-{gamma} (IFN-{gamma})-release assays provide more-accurate diagnosis of Mycobacterium tuberculosis infection than conventional skin tests but do not differentiate between latent and active disease. However, another cytokine — interleukin-2 (IL-2) — also plays an important role in the cellular immune response to mycobacteria. Might measuring both IFN-{gamma} and IL-2 release improve determination of disease stage?

To find out, researchers in Italy conducted a study involving 20 uninfected healthy controls, 20 skin test–positive patients with latent tuberculosis (TB), and 20 patients with culture-confirmed active TB. They used a modified QuantiFERON-TB Gold In-Tube test to measure IFN-{gamma} and IL-2 levels in each blood sample after 18 and 72 hours of incubation.

IL-2 and IFN-{gamma} levels remained very low at 18 and 72 hours in the controls. IFN-{gamma} levels at 18 and 72 hours in the patients with latent TB were significantly higher than those of controls and were indistinguishable from those of the patients with active TB. However, IL-2 levels at 18 hours were significantly higher in the patients with latent TB than in patients with active TB or controls; by 72 hours, the difference was much more pronounced. An IL-2 threshold of 2.0 U/mL at 72 hours showed 90.0% sensitivity and 97.5% specificity for discriminating patients with latent TB from those with active TB or controls.

Comment: The differential release of IL-2 and INF-{gamma} in latent and active TB can be explained by the predominance of different types of memory T cells, depending on the stage of disease. Measuring the responses of both cytokines appears to be essential, because considering IL-2 alone would miss the active TB cases.

The impressive results of this preliminary investigation must be confirmed in larger studies before a breakthrough in TB diagnosis can be announced.

— Thomas Glück, MD

Published in Journal Watch Infectious Diseases August 4, 2010
Citation(s):

Biselli R et al. Detection of interleukin-2 in addition to interferon-{gamma} discriminates active tuberculosis patients, latently infected individuals, and controls. Clin Microbiol Infect 2010 Aug; 16:1282.

* Medline abstract (Free)

https://docs.google.com/fileview?id=0B278nGJMQBk7Y2JlNmFjY2UtODEyMC00OWIzLWI5OTAtMjlmYWM3MWM5YzZk&hl=zh_TW

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