Rate of extrapulmonary TB highest among blacks
Although tuberculosis (TB) most often affects the lungs, it can infect other parts of the body such as the lymph nodes and various organs. This "extrapulmonary" type of the disease is usually a signal of a compromised immune system, such as from HIV infection, which increases the risk for this form of TB. A new study has found that black men and black women experience the highest incidence of extrapulmonary TB. They are also more likely than nonblacks to develop this form of the disease when they are infected with TB. Researchers compiled data on all TB cases reported in the State of Tennessee during a 6-year period from 2000 to 2006. They categorized patients into one of three TB groups: pulmonary, extrapulmonary, or both. They also collected information on race, sex, and risk factors for extrapulmonary TB.
A total of 2,142 cases of TB were reported to the State health department. More than a quarter of these (26.3 percent) were extrapulmonary in nature. Black men had the highest annual rate of extrapulmonary TB at 5.93 per 100,000 people. Next were black women (3.21), followed by nonblack men (1.01), and nonblack women (0.58). Overall, blacks had higher rates of this form of TB compared with nonblacks at all ages. In addition, blacks with TB were more likely to be diagnosed with extrapulmonary TB (31.5 percent) than nonblacks (24.3 percent).
Factors independently associated with a higher risk for extrapulmonary TB were having HIV infection and being of foreign birth. Interestingly, alcohol use was significantly associated with lower odds for extrapulmonary TB. The researchers propose several reasons for why this form of TB is so prevalent among blacks. These include higher rates of TB complicating HIV infection, and differences in exposure to TB, access to medical care, and socioeconomic status. The study was supported in part by the Agency for Healthcare Research and Quality (HS13833).
See "Black race, sex, and extrapulmonary tuberculosis risk: An observational study," by Christina T. Fiske, M.D., Marie R. Griffin, M.D., M.P.H., Holt Erin, and others in BMC Infectious Diseases 10(16), pp. 1-8, 2010.
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