What would you think if your doctor came at you with a humongo hypodermic needle like you see in those vintage mad-scientist movies, and he told you that the doctors in his family had used it since 1890? Well, it’s only a slight exaggeration to say that’s essentially what happens every time we get a TB test.
Someday soon, however, we should get the advantage of 21st-century medical science: The FDA just approved a new test for mycobacterium tuberculosis infection, or TB. It’s a blood test looking for immune response to proteins from the TB bacteria, not unlike today’s basic test for HIV infection. Also like current HIV testing, the result is not immediate, but the test is more than 99% accurate.
The present version of the century-old skin test (Mantoux, or “man-too”) makes six tiny injections in your arm. Several days later, you must return to have the results evaluated by a health care professional, whose subjective judgment may be inaccurate up to 50% of the time. Further, the Institute of Medicine says 30% of persons tested don’t come back for their results – just like current HIV testing. For HIVers with damaged immune systems, it gets more complicated because they may not react in the usual way.
Initially, QuantiFERON-TB GOLD will be marketed by its manufacturer, Cellestis Inc. of Valencia, Calif., to health departments, prisons, and militaries. Eventually, it also should be in use by private physicians. After 100 years, it’s about time!
This article appears in January 28 • 2005.