Tuberculosis: Part 2

by Food and Drug Administration (FDA)

(Page 2 of 3)

Increasing enrollment of the elderly in nursing homes is also leading to the rising incidence of TB. One study found that male nursing home patients in Arkansas developed TB at a rate 10 to 30 times the rate of men of similar ages living in other circumstances. Schools have also been implicated as a source of outbreaks, since cases among children rose 16 percent in 1989.

Other factors leading to a greater number of cases — either by increasing the risk of exposure to TB or affecting the body's ability to fight the disease — are crowded living conditions, poor nutrition, poverty, stress, drug use, alcoholism, and immigration from areas where TB is common.

Testing for TB

Gone are the days when all American school children were routinely tested for TB. Who can forget the tine test, in which a four-pronged device containing a substance called tuberculin punctured tender forearms? Or how the school nurse examined those forearms a few days later?

Though TB testing was mandatory in schools throughout the United States in the past, many of those programs were allowed to lapse as TB became less of a public health threat. "Because of some recent outbreaks, more and more school systems, which for a while had deemphasized TB testing for both faculty and students, have now reinitiated testing, though that varies from area to area," says Donald Kopanoff, associate director of CDC's division of tuberculosis control.

Though the tine test is still used in screening large populations with low exposure to TB, experts believe the Mantoux test — in which a substance called purified protein derivative (PPD) is injected under the skin of the forearm and examined about 48 to 72 hours later — is more reliable. A thickening of the area suggests that the person may have been infected with TB bacteria. But this doesn't necessarily mean that the person has the active disease. (It is also possible that the reaction may be due to infection with nontuberculous but related bacteria.)

Testing Recommendations

Common sense would dictate that anyone with symptoms or who has been in close contact with someone with active TB should have a skin test, which can be administered either by private physicians or in public clinics.

TB skin-testing is mandatory in certain states and counties for immigrants and students from Africa, Asia and Latin America, as well as for personnel in schools, hospitals, correctional facilities, food-handling establishments, group homes, child-care facilities, and substance abuse centers.

Skin tests are also recommended for our senior citizens. "Elderly people, especially those in nursing homes, who happen to be infected, but have not developed [active] disease, may, in fact, as they become more debilitated or develop some other concomitant illness, have that infection break down and develop into active disease," says Kopanoff. "Since they're around a lot of other elderly people who are also at high risk of becoming infected and developing active TB, it's pretty much mandatory for both employees and new clients to be skin-tested at the time they come on board. Depending upon the risk of TB in the general community surrounding the nursing home, individual administrations have to decide how often they're going to do repeat skin tests, especially for the employees."

At present, screening of children entering kindergarten or day-care centers is not required in all school jurisdictions, but CDC recommends that school children be tested for TB to ensure that all U.S. citizens are tested at least once in their lifetimes.

Diagnosis

If a person has a significant reaction upon being tuberculin skin-tested for the first time, additional laboratory and x-ray examinations are necessary to determine if the individual has active TB. Once infected, most persons will generally test positive for the rest of their lives.

TB can mimic some other diseases, such as pneumonia, lung abscesses, tumors, and fungal infections, or occur along with them. For proper diagnosis, therefore, a doctor will rely on symptoms and other physical signs, a person's history of exposure to TB, and x-rays that may show evidence of TB infection, usually in the form of lesions or cavities in the lungs. TB bacilli grown in cultures of sputum or other specimens provide a positive diagnosis.

How TB Is Treated

Isoniazid, or INH, is TB's wonder drug. Inexpensive, effective, easy to take, it can both prevent and cure TB. CDC and the American Thoracic Society recommend preventive treatment, which consists of one pill of INH each day for at least six months, for individuals who have:

• close contact with a person with infectious TB
• positive tuberculin skin test reaction and an abnormal chest x-ray that suggests inactive TB
• a tuberculin skin test that converted from negative to positive within the past two years
• a positive skin test reaction and a special medical condition (for example, AIDS or HIV infection or diabetes) or who is on corticosteroid therapy
• a positive skin test reaction, even with none of the above risk factors, in someone who is under 35.

About the Author

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