New Tuberculosis Blood Test Spots Hidden Infection

It's an improvement on traditional skin screen, study finds

THURSDAY, March 15, 2007 (HealthDay News) -- Two new interferon-gamma blood tests were able to detect latent tuberculosis infection in hundreds of people exposed to a person with contagious TB -- even though traditional tuberculin skin tests (TST) did not, Dutch researchers report.

"One-third of the world's population is believed to harbor latent TB infection," study author Dr. Ailko Bossink said in a prepared statement. "Approximately 5 to 15 percent of immunocompetent persons with latent TB infection will develop TB disease."

The researchers studied 785 supermarket customers who'd been in contact with a TB-infected supermarket employee who'd been contagious since February 2004. The study began in early 2005.

"Among the 785 study participants, TB skin test results were associated with age, whereas positive interferon-gamma blood test assay results were significantly associated with cumulative shopping time [exposure]. TB skin test results were not associated with any measure of exposure to the index case in the supermarket," Bossink said.

The two interferon-gamma release assays (IGRAs) used in the study measured response to an antigen highly specific for Mycobacterium tuberculosis. One of the tests -- QuantiFERON-TB Gold -- has been approved for use in the United States. The other test has been approved for use in Europe.

The study is published in the second issue for March of the American Journal of Respiratory and Critical Care Medicine.

More information

The American Lung Association has more about TB.

SOURCE: American Thoracic Society, news release, March 2007
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