Latent tuberculosis, or latent TB, often leads to full blown active tuberculosis. Until now, patients have had to ingest approximately 270 doses of a single drug over a nine month period which can be a painstaking procedure. However now, after a decade of trials, a new combo therapy involving two drugs taken 12 times over three months may do the same job. In addition the shorter regiment was easier for patients to complete, adding to its effectiveness.

In a telephone press conference, officials of the CDC, which sponsored the trial, said the agency will be revisiting its latent TB guidelines in light of the findings.

The combination of rifapentine (Priftin) and isoniazid (Nydrazid) was as effective in preventing active TB as nine months of daily isoniazid alone, according to Timothy Sterling, MD, of Vanderbilt University in Nashville, Tennessee at the yearly meeting of the American Thoracic Society.

The shorter course is now a useful alternative to the controversial isoniazid regimen, which has been the standard therapy for people with latent TB who are at risk of active disease, Sterling said at the annual meeting of the American Thoracic Society.

The "PREVENT TB" trial enrolled 8,053 people with latent TB but who were regarded as being at high risk of developing active disease, and randomly assigned them to one of the two regimens.

The participants, mostly from the U.S. and Canada, were followed for 33 months from the date of enrolment with the primary goal of seeing how many developed active disease, assessed by a cumulative TB rate. The medications were taken monthly under direct observation.

Sterling reported that 82% of those getting the two-drug regimen completed the 33 months of follow-up, compared with 69% of those getting isoniazid extensive 270 dose program.

Latent tuberculosis is where a patient is infected with Mycobacterium tuberculosis, but does not have active tuberculosis disease. Patients with latent tuberculosis are not infectious, and it is not possible to get TB from someone with latent tuberculosis.

The main risk is that approximately 10% of these patients will go on to develop active tuberculosis at a later stage of their life. This is particularly true if there is development of a disease affecting the immune system, such as AIDS or a disease whose treatment affects the immune system. In some people, TB bacteria overcome the defenses of the immune system and begin to multiply, resulting in the progression from latent TB infection to active TB disease. Some people develop active TB disease soon after infection, while others develop active TB disease later when their immune system becomes weak.

The identification and treatment of people with latent TB is an important part of controlling this disease. If TB disease is suspected, persons should be referred for a complete medical evaluation. If it is determined that a person has active TB disease, therapy is given to treat it. TB disease is a serious condition and can lead to death if not treated.

Sources: The American Thoracic Society, U.S. National Library of Medicine National Institutes of Health and Centers For Disease Control And Prevention

Sy Kraft

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