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Tuberculosis today: Fighting an ancient adversary

Tuberculosis (TB) has been killing people for a long time. Egyptian mummies from 2400 BCE show signs of the disease. And despite therapeutic advances over the years, TB isn’t going away any time soon.

Today, about 2 billion people, roughly one-third of the world’s population, are infected with TB, and about 2 million people die each year from the active disease. The incidence of TB is particularly high in developing nations because of poor sanitation, poor nutrition, and co-infection with such diseases as HIV/AIDS. (See Tuberculosis in the United States by clicking on the PDF icon above.)

What is TB?

An infectious disease caused by the bacillus Mycobacterium tuberculosis, TB usually affects the lungs but may involve any organ and may infect anyone at any age. The bacillus lodges in the lungs and is picked up by the bloodstream and circulated to other organs, where it may stay dormant.

M. tuberculosis spreads from person to person through the air. People become infected by breathing the same air as a person with active TB. Fortunately, M. tuberculosis isn’t an easy bug to catch; contracting the disease requires hours of close contact.

When TB is latent

People with latent, or inactive, TB are infected with the bacterium but don’t have the active infectious process or any symptoms of TB. The bacterium can live in a person undetected for years, until a TB test detects it or active, contagious TB develops.

Only about 10% of those diagnosed with latent TB develop active TB. Many times, the active disease develops because of a coexisting immunosuppressive disease.

Latent TB isn’t reportable because it presents no public health threat. If a person with latent TB has contact with people who have active TB, the health department may follow up. If latent TB in a healthcare worker can be linked to an identifiable case of TB in a facility, precautions may have been breached.

When TB becomes active

If not treated in the latent stage, TB can become active. Active TB is contagious only if it’s in the lungs or laryngeal tract. Whether or not it’s contagious also depends on the length of time of the illness, the number of organisms on smear and culture, and the patient’s ability to cough or sneeze the microorganisms out into the air. By law, active TB must be reported.

Unlike patients with latent TB, most patients with active TB are very sick and hospitalized. The typical signs and symptoms of active TB include fever, chills, night sweats, cough, and coughing up blood. Patients may also experience fatigue for no apparent reason and have an unexplained weight loss and shortness of breath. Specific signs and symptoms vary from patient to patient.

In the hospital, a patient with active TB must be isolated from other patients in a negative-airflow room under airborne isolation precautions. Healthcare workers entering the room should use an N-95 respirator for protection. The Occupational Safety & Health Administration requires that these respirators be fit-tested before initial use. There’s no regulation for visitors, but a visitor should maintain precautions, and you should offer an N-95 respirator. If the patient isn’t in the hospital, tell him to stay home and not return to work until he has clearance.

Who’s at risk?

TB can strike anyone, but people at high risk include those who stay in countries with a high prevalence of TB, anyone exposed to a person with active TB, the homeless, those in correctional facilities, the immunocompromised, substance abusers, people with a chronic illness, the elderly, and those who are age 4 and younger.

In the United States, foreign-born people and members of racial and ethnic minorities are most affected. In 2006, the TB rate among the foreign-born was 9.5 times higher than the rate among those born in the United States. The TB rates among African Americans, Asians, and Hispanics were also
disproportionately higher than the rates among whites. Our inability to effectively address these persistent disparities threatens progress toward eliminating TB in the United States.

Areas with the highest risk include Mexico, Africa, Russia, the Pacific islands, and Asian countries.

Testing for TB

Typically, testing for TB begins with a purified protein derivative (PPD) skin test. (See Guidelines for PPD testing by clicking on the PDF icon above.) If a patient has a positive PPD test result, the next steps are a thorough health history and a chest X-ray.

The health history should include a review of TB symptoms and risk factors, such as substance abuse, human immunodeficiency virus (HIV) infection, chronic illnesses, smoking, medication history, and travel to high-risk countries. Ask, too, about the possibility of close contact with another person who has active pulmonary TB. Patients with latent TB have a positive PPD test result but no symptoms of TB and no signs of TB on a chest X-ray.

If the PPD test result is negative, the clinician may order a second test 1 to 3 weeks later because, in some people infected with M. tuberculosis, the ability to react to tuberculin wanes over the years. A second skin test may boost their ability to react. This two-step skin testing is recommended for immuno­compromised patients, those who have not had a skin test in the past 5 years, and those who don’t remember being tested.

The bacille Calmette-Guérin (BCG) vaccine, which is used in many countries outside the United States, can also affect the results of a PPD test. Patients who have had the vaccine may have a scar on the left upper arm, but such a scar or documentation of BCG doesn’t mean the patient is protected against TB. The BCG vaccine can yield a false-positive PPD test result. However, the more time that passes between the BCG vaccination and the PPD test, the more likely a positive result is truly a positive result. If a patient with a history of BCG vaccination has a positive PPD test result, the next test is the same as it would be for someone who has never had a BCG vaccination: a chest X-ray. (See Beyond PPD: A new diagnostic tool for TB by clicking on the PDF icon above.)

Diagnosing active TB

A patient with a positive PPD test result, symptoms of TB, and normal chest X-rays is usually considered to have active extrapulmonary TB (TB that’s not in the lungs). In some cases of extrapulmonary TB, a contact investigation may not be needed. In a patient with a positive PPD test result and symptoms of TB, a chest X-ray that is suspicious for pulmonary TB may show infiltrates, a defined cavitary lesion, or a diffuse miliary pattern.

Even when TB appears to be extrapulmonary, a clinician will order sputum specimens to assess for acid-fast bacilli (AFB) and determine if the infection has entered the lungs. Obtain a specimen each morning for 3 consecutive days; morning is best because secretions pool during the night. If the patient can’t produce a specimen by coughing, try to induce a specimen. The fact that a patient can’t produce sputum with the normal coughing mechanism is actually good: It means he can’t cough out—and spread—the pathogen.

The lab will determine if the specimen contains AFB and, using a DNA probe test, if the AFB is M. tuberculosis. Keep in mind that M. tuberculosis is only one member of the AFB family. And it has lots of “cousins.” Only the lab can identify the exact AFB family member. From a public health standpoint, only M. tuberculosis is a cause for concern.

Treating latent TB

The drug of choice for latent TB is isoniazid (INH). The usual adult dosage is 300 mg daily for 9 months, but the specific dosage for a particular patient is based on body weight. If the patient has a history of I.V. drug use, alcohol use, or hepatitis or if the patient is elderly, a prescriber may order baseline liver function tests to evaluate the liver’s ability to tolerate INH.

The adverse effects of INH mimic the signs and symptoms of hepatitis: right-upper-quadrant abdominal pain, nausea, vomiting, yellowing of the sclera, and darkening of the urine. Be sure to teach patients about latent TB and these adverse effects of treatment. To counter the adverse effects, some clinicians order 25 mg a day of oral vitamin B6 (pyridoxine).

Treating active TB

If the patient is symptomatic and has AFB in the sputum (or other body fluid), the clinician will start drug therapy, even before the specific AFB organism is identified. If the organism isn’t M. tuberculosis, the prescriber can discontinue the drug.

Before starting drug therapy, however, the clinician should obtain a baseline metabolic panel, a complete blood count, Snellen eye test results, and the results of an Ishihara color-blind test. Because of the prevalence of TB in HIV-infected patients, an HIV test is also recommended for patients with active TB.
To prevent drug resistance, clinicians prescribe four-drug therapy. The four drugs of choice are INH, rifampin, ethambutol, and pyrazinamide. Dosages depend on the patient’s weight. To counter the adverse effects of these drugs, such as neuropathy, some clinicians order vitamin B6 (pyridoxine). Before starting drug therapy, teach the patient about the possible adverse effects. Rifampin, for example, can turn urine a distinct orange color, and can stain contact lenses. Such effects can cause anxiety if the patient isn’t prepared for them.

To ensure that the four drugs are effective, the lab runs sensitivity tests for M. tuberculosis. The preferred outcome is that the organism is sensitive to all four drugs. If not, the prescriber will change the regimen.

Depending on the degree of infection and the ability of the drugs to treat the disease, therapy usually lasts 6 to 9 months. In the future, PA-824, an antibiotic currently in clinical trials, may be able to shorten treatment time.

Dealing with drug-resistant TB

Multidrug-resistant TB (MDR TB) is TB that resists the two best front-line drugs, INH and rifampin. In 2000, the estimated number of people with MDR TB was more than 250,000 worldwide.

For people with MDR TB, the treatment options are less effective. MDR TB is a particular concern for patients with HIV infection.
Resistance can develop when drugs are misused or mismanaged. Mismanagement includes patients not completing the full course of therapy and prescribers providing the wrong treatment or dosage. Sometimes, the problem is that the drugs aren’t absorbed completely. Patients may also develop MDR TB if they contract active TB again after completing treatment.

A rare type of MDR TB is called extensively drug-resistant TB (XDR TB). This infection resists almost all TB drugs, including INH and rifampin. XDR TB also resists the best second-line drugs, the fluoroquinolones, and at least one of three injectable drugs, such as amikacin, kanamycin, or capreomycin.

Some TB programs have shown that XDR TB can be cured in about 30% of patients. Successful treatment depends on the extent of the resistance, the severity of the disease, and the status of the patient’s immune system. The signs and symptoms of XDR TB mirror those of other strains. Fortunately, the risk of acquiring XDR TB in the United States appears to be low: Between 1993 and 2006, only 49 cases were reported.

Monitoring the patient’s therapy

Throughout treatment for pulmo­nary TB, serial sputum specimens are obtained to document the conversion from positive to negative specimens. Also, throughout treatment, patients need to be monitored. To ensure patient adherence, drugs for TB should be given by a method known as directly observed therapy (DOT). DOT means that a healthcare worker gives the drugs directly to the patient and watches the patient take them.

You can also promote patient adherence by providing incentives for continuing treatment and participating in the case management of the disease. Incentives will vary from patient to patient and should reflect a patient interest, such as a hobby. In one instance, a patient who remained faithful to treatment was given a pool cue as a reward. (See The role of local health departments by clicking on the PDF icon above.)

Meeting the challenges

Identifying and treating TB still pose infection-control and public-health challenges in the 21st century. And individual patients with TB present their own set of challenges—financial, social, and cultural.

To meet these challenges, hospitals and local health departments must work together. In your local health department, you can find a wealth of information and resources. And public health departments can find great support in local hospitals and their infection-control departments. Working together, hospitals, nurses, physicians, patients, families, and public health providers can ensure effective care for patients with TB and effective protection for the community.

Selected references

American Thoracic Society. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med. 2000;161:S221- S247. Available at: www.cdc.gov/mmwr/preview/mmwrhtml/rr4906a1.htm. Accessed September 10, 2007.

Daley CL, Gotway MB, Jasmer RM. Radiographic Manifestations of Tuberculosis:
A Primer for Clinicians. Francis J. Curry National Tuberculosis Center. Available at: http://www.nationaltbcenter.edu/products/
tbradiographic.cfm. Accessed September 10, 2007.

Francis J. Curry National Tuberculosis Center. Available at: www.nationaltbcenter.edu. Accessed October 20, 2009.

Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings. MMWR Recomm Rep. 2005 Dec 30;54(RR-17):1-141. Available at: www.cdc.gov/mmwr/preview/mmwrhtml/rr5417a1.htm. Accessed September 19, 2007.

Guidelines for the Investigation of Contacts of Persons with Infectious Tuberculosis: Recommendations from the National Tuberculosis Controllers Association and CDC. MMWR 2005 Dec 16; 54(RR-15):1-37. Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5415a1.htm. Accessed October 20, 2009.

National Jewish Medical and Research Center. About nontuberculous mycobacteria (NTM). Available at: www.njc.org/disease-info/
diseases/nts-mycobac/about/index.aspx. Accessed September 10, 2007.

Treatment of tuberculosis. MMWR Recomm Rep. 2003 Jun 20;52(RR-11):1-77. Available at: www.cdc.gov/mmwr/preview/mmwrhtml/
rr5211a1.htm. Accessed September 19, 2007.

Tuberculosis. Available at: www.nlm.nih.gov/medlineplus/tuberculosis.html. Accessed September 10, 2007.

Updated Guidelines on Managing Drug Interactions in the Treatment of HIV-related Tuberculosis. MMWR 2008 Feb 1; 57(04):98.

World TB today. MMWR Recomm Rep. 2007 March 23;56(11);245-250. Available at: www.cdc.gov/mmwr/preview/mmwrhtml/mm5611a1.htm. Accessed September 19, 2007.

When the article was written, Rebecca Ruppert, RN, was a Communicable Disease RN in the Tuberculosis Program of the Marion County Health Department in Salem, Oregon. The author does not have any financial arrangements or affiliations with any corporations offering financial support or educational grants for continuing nursing education activities.

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