"WALKING" TB -- YOU MAY HAVE IT AND NOT KNOW IT

"WALKING" TB -- YOU MAY HAVE IT AND NOT KNOW IT Each year, about 11 million Americans are diagnosed with what’s known aslatent tuberculosis, which means that someone with active TB has infected them with a dormant form of the disease. This latent form of TB -- which is far and away the most common kind of TB here in the US -- could develop into a much more serious active form at some point in their lives. What’s worse: If a person has latent TB and it develops into the active form, his/her disease suddenly becomes contagious and he is capable of infecting others. You’d think that people with latent TB would be worried about it -- and I am sure that some are. But apparently not all of them are, since about half of the people who get this diagnosis don’t even complete the treatment required to cure their illness! Surprised? I have to admit that I was, too -- though less so when I learned that people with latent TB have no symptoms. Plus, the traditional form of treatment for latent TB is long and grueling, requiring many doctor visits over the course of nine months and 270 total doses of daily medication. Now the better news -- a large-scale, CDC-sponsored study has shown that a new, far simpler three-month treatment for latent TB is just as safe as the horrid nine-month course of treatment I described above, and (unsurprisingly) the study also found that patients are more likely to stick with it. WHY IS INACTIVE TB SUCH A BIG DEAL? Let’s back up for a minute to properly understand the importance of this news. Active TB is a contagious disease that was once a major health problem. Up until the mid-20th century, people with active TB suffered from debilitating symptoms, such as chronic cough, fatigue, unexplained weight loss, fever and night sweats. They often were sent away for months -- sometimes a year or longer -- to try to recover in the company of other TB patients in isolated sanitariums. Luckily, most developed countries have dramatically reduced cases of active TB thanks to vaccines, so now it is quite rare. Latent TB has also been on the decline here in the US -- but it remains a problem. An estimated 4% of the US population tests positive for latent TB, and it is estimated that as many as one-third of the world’s population actually has latent TB, an alarming prospect if even a small percentage of those become active. To learn more about latent TB -- and about the new, easier treatment for it -- I consulted infectious disease researcher Timothy R. Sterling, MD, the principal investigator in the study and a professor of medicine at Vanderbilt University Medical Center in Nashville. BY THE NUMBERS Dr. Sterling told me that the only ways to diagnose an infection of latent TB are with a tuberculin skin test or an interferon blood test. Of course, not everyone is required to get tested. Usually, only people who work in close contact with others and are therefore at higher risk of contracting and spreading infection -- such as teachers, health-care workers and prison guards -- must get tested. Nobody is likely to suggest out of the blue that you get tested, but if you’re curious -- or experiencing TB-like symptoms -- you can always ask your doctor for a test. Of the roughly 11,000 cases of active TB diagnosed in this country each year, Dr. Sterling said, studies suggest that approximately 70% are activations of previously latent infections (though, he said, it’s hard to know for sure). Whether or not latent TB develops into active TB depends on the strength of the person’s immune system. Most people are healthy enough to fight it off. The people at highest risk tend to be the most medically vulnerable people, including those with weakened immune systems... those who have an underlying disease such as diabetes or HIV, rheumatoid arthritis or psoriasis.... those who take drugs to treat Crohn’s disease... those who are on chemotherapy... and those who are elderly or malnourished or are living in extended-care facilities, such as nursing homes. Therefore, many people who develop active TB often get hurt by a double whammy -- they have to suffer from the symptoms of TB and the TB can cause complications to the health problems they already have. SHORTER, EASIER: THE NEW TREATMENT In the 10-year, multi-country PREVENT TB trial, Dr. Sterling and his team gathered a total of 8,053 people with latent TB. Researchers randomly assigned them to receive either the standard treatment (daily doses of the drugisoniazid for nine months) or a three-month treatment consisting of higher doses of the same drug and an additional TB fighter, rifapentine, which were both administered weekly (12 total doses). Dr. Sterling presented these study results at an international conference of the American Thoracic Society in May 2011. Dr. Sterling and his colleagues found that when it came to the new treatment... It was just as effective. Few cases of active TB developed in either group. More people stuck with it. More than eight out of 10 participants (82%) completed the shortened treatment, compared with only 69% with the standard therapy. It was just as safe. The new three-month treatment showed lower rates of liver toxicity as a side effect, but higher levels of toxicity in other areas. So the toxicity profiles of the new and traditional treatments were similar, according to Dr. Sterling. THE GOAL: ERADICATE TB IN THE US The public health goal is to get rid of TB altogether, which can happen only if both the latent and active forms are eliminated. Given the promising results of this study, the CDC is already working on new guidelines to recommend the use of the shorter treatment here in the US. Using these guidelines, the new treatment is expected to be available as soon as next year. This is great news that may bring us closer to a day when TB goes the way of polio and becomes a problem that we really don’t have to worry about anymore.

Source:

Timothy R. Sterling, MD, professor of medicine, division of infectious diseases, Vanderbilt Institute for Global Health, Vanderbilt University, Nashville.