On May 7, 2019, the Centers for Disease Control and Prevention (CDC) updated guidelines for Tuberculosis (TB) testing of healthcare workers including EMS personnel. This was updated on March 8, 2021. One of the most significant changes was that annual TB testing of health care personnel is no longer recommended. The new guidelines call for all U.S. health care personnel to be screened for TB upon hire including a risk assessment, TB symptom evaluation and TB testing. Following that, annual TB testing of health care personnel is not recommended unless there is a known exposure or ongoing transmission. Instead, employees should receive annual TB education that includes information on TB risk factors, the signs and symptoms of TB disease, and TB infection control policies and procedures.
What is Tuberculosis?
Tuberculosis is an infection caused by the bacteria Mycobacterium tuberculosis.
Where is Tuberculosis Found?
TB is found worldwide. While relatively uncommon in the United States, it has been estimated that approximately one-fourth of the world population has TB infection. In excess of 95% of TB cases and deaths occur in developing countries.
Specifically, 88% of new TB cases worldwide come from 30 countries that have a high TB burden. Eight countries account for two thirds of the total new TB cases:
- India (highest),
- The Philippines,
- Bangladesh, and
- South Africa.
Fortunately, the incidence of TB worldwide is falling at about 2% per year. In 2019, the United States reported only 8,916 cases new TB cases (2.7 per 100,000 population).
Who Is At Risk for Tuberculosis?
Tuberculosis is primarily a disease of adults but can affect all age groups. Patients with active HIV infections and those on immunosuppressive therapy (e.g., cancer patients) are significantly more likely to contract TB. Other risk factors include people with tobacco use disorder, alcohol use disorder, diabetes, low body weight and malnutrition. Also, infants and children less than four years of age are at increased risk due to an immature immune system.
What Are the Signs and Symptoms of TB Infection?
TB is primarily a respiratory disease and is spread through the air. The infected person spreads the bacteria when they cough, speak, or sneeze. People in close proximity may then inhale the TB bacteria and become infected. Interestingly, not everyone infected with TB bacteria become sick. Two TB-related conditions exist:
- Latent TB infection (LTBI). People with LTBI are infected with M. tuberculosis but they do not have TB disease. They do not have any of the signs and symptoms of TB disease and they cannot spread M. tuberculosis to others. They usually have a positive TB skin test or a positive TB blood test. Only 5-10% of people with LTBI later develop TB disease if they do not receive treatment. However, many people who have latent TB infection never develop TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease.
- TB disease. TB disease, also called “active TB,” is a potentially serious infectious disease caused by infected with M. tuberculosis that primarily affects the respiratory tract (lungs). The signs and symptoms of TB disease include:
- Persistent cough lasting three weeks or longer
- Chest pain
- Coughing up sputum or blood (hemoptysis)
- Weakness or fatigue
- Weight loss
- Loss of appetite
- Fever (often recurrent)Night sweats
In some cases, TB infection can spread outside of the lungs and is called extrapulmonary TB (EPTB). EPTB infection can involve the lymph nodes (lymphadenitis), pleura (pleuritis), the meninges (meningitis), abdomen (peritonitis), genitourinary tract, and bone. TB infection of the spine is called Pott’s disease. Miliary TB occurs when the TB bacteria are spread through the blood affecting both pulmonary and extrapulmonary sites. Approximately 10% of all TB cases have both pulmonary and extrapulmonary TB.
How is TB Diagnosed?
There are several ways to diagnose TB. The most common methods are skin testing and blood testing.
- Skin test. The skin test, also called a Mantoux tuberculin skin test (TST), is commonly used. For this test, a small amount of fluid called tuberculin or purified protein derivative (PPD) is injected into the skin (intradermal) of the volar forearm. This fluid contains inactivated purified protein fraction obtained from human strains of M. tuberculosis and is antigenic (will invoke an immune response). The injection site is checked at 72 hours post-injection. If there is an induration (not redness) of 10 millimeters or more at the injection site, the test is deemed positive.
- Blood test. There are two TB blood tests approved for use in the United States: QuantiFERON® and T-Spot®. These tests detect and measure the body’s cell-mediated immune response (interferon gamma) following exposure to antigens from M. tuberculosis. A positive test means that the person has been infected with TB bacteria and additional tests are needed to determine if the person has LTBI or TB disease. A negative TB blood test means that the person did not react to the test and that latent TB infection or TB disease is not likely.
- Chest x-ray (CXR). Chest x-rays are frequently used to determine whether or not there is pulmonary infection associated with a positive TB test. In some instances, an abnormal chest x-ray may be the first indicator of TB in a patient. A negative chest x-ray does not exclude the presence of TB infection in other parts of the body.
- Lab testing. Microscopic examination of expectorated sputum from an infected patient may demonstrate the presence of M. tuberculosis bacteria. Specialized blood cultures for M. tuberculosis and similar bacteria are also available.
Is There a Vaccine for TB?
There is a vaccine for TB but it is not used in the United States. The vaccine, called the Bacillus Calmette–Guérin (BCG) vaccine, is primarily used in countries where TB and leprosy are common (primarily in South America and Europe).
The vaccine is generally effective and safe but can cause pain and scarring at the injection site. Persons who received the BCG vaccine will test positive during subsequent TB testing and require specialized evaluation.
What is the Treatment for TB?
LTBI is typically treated with a 3-4 months course of isoniazid (INH), rifapentine (RPT), or rifampin (RIF). TB disease is typically treated using several drugs for 6 to 9 months. The first-line anti-TB agents are isoniazid (INH), rifampin (RIF), ethambutol (EMB), and pyrazinamide (PZA). There are several strains of the M. tuberculosis bacteria that have become resistant to many of these drugs (multi-drug resistant) and specialized treatment strategies are required. Multi-drug resistant TB is most commonly seen in patients with HIV infection or those with immunosuppression.