Tuberculosis Section (TB)

Disease Information

Transmission

TB is a disease that primarily affects the lungs, but can affect any part of the body. A germ called Mycobacterium tuberculosis causes the disease.

TB is spread through the air when an infected person sprays out droplets by coughing, speaking or singing. Some droplets don't fall to the ground but remain suspended in the air, then break apart and leave very tiny germs. These germs must be inhaled and get down into the alveoli (tiny air sacs) of a person's lungs for someone to become infected.

Symptoms of Tuberculosis

• Productive cough - usually lasting more than 3 weeks
• Unexplained fever
• Night sweats
• Unintentional weight loss
• Loss of appetite
• Extreme tiredness
• Coughing up blood or blood streaked sputum

Tuberculin Skin Test (TST)

The tuberculin skin test is used to determine whether a person has become infected with the TB germ. It can take from 2 to 12 weeks after exposure to the TB germ for the person's immune system to react to the TST. This means a second TST may be needed for complete evaluation after exposure during a contact investigation.

Administration and Reading the Tuberculin Skin Test

To perform the TST, purified protein derivative (PPD) solution is injected right under the skin in a person's arm. A trained professional checks the arm for a reaction 48 - 72 hours later. Any induration (raised, hardened area) will be measured and recorded. Redness at the site of injection is not to be considered or measured. The measurement of induration plus a person's risk factors for TB will determine whether a skin test is interpreted (see chart below) as positive or negative. A person with a positive skin test needs to be evaluated to determine if the person has latent TB infection (LTBI) or active TB disease. This evaluation usually consists of a medical history/exam, a chest x-ray and possibly the collection of sputum specimens. A person who has had a positive skin test should not have any more skin tests done and should carry documentation recording the date & place of the test, the measurement and any treatment.

Interpretation of the Tuberculin Skin Test

• HIV positive persons
• Recent contacts to a TB case
• Persons with fibrotic changes on chest radiograph consistent with old TB
• Persons with organ transplants, and other immunosuppressed persons (those receiving the equivalent of >15 mg/day of prednisone for > 1 month

• Recent immigrants (<5 years) from high-prevalence countries
• Injection drug users
• Residents and employees of high-risk congregate settings (e.g., correctional facilities, nursing homes and other long-term facilities for the elderly, homeless shelters, residential facilities for AIDS patients, hospitals and other health care facilities)
• Mycobacteriology laboratory personnel
• " Persons with clinical conditions that place them at high risk of progression to TB disease: silicosis, diabetes, chronic renal failure, leukemias and lymphomas, carcinoma of the head, neck or lung, weight loss of >10% of ideal body weight, gastrectomy, jejunoileal bypass, substance abuse, infection with M.tuberculosis within the last two years, chronic malabsorption syndromes or candidates being considered for injectable Remicade (Infliximab) prior to the initiation of therapy
• Children <4 years of age, or children and adolescents exposed to adults in high-risk groups

• Persons with no know risk factors for TB

Latent TB Infection (LTBI)

In Latent TB Infection, a person has inhaled the germ and has become infected but the body's immune system has built a wall around the germs. The germs are dormant or sleeping and do not grow and multiply. The person is not sick and does not have symptoms of TB. The person will usually have a positive reaction to a tuberculin skin test but will have a normal chest x-ray and will not have any symptoms of the disease. A person with LTBI cannot give the germ to anyone else. There is a 10% chance of becoming sick with active TB disease over a lifetime if medication is not taken. Medication is available to reduce the chance of a person with LTBI from becoming sick with active TB disease.

Latent TB Infection (LTBI) is usually treated with one medication (Isoniazid) taken every day for 9 months. Sometimes Vitamin B6 is given at the same time.

Active TB Disease

Active TB disease occurs in a person infected with the TB germ whose body's immune system is not strong enough to either build a wall around the germs or to keep the wall from breaking down. When this happens, the germs "wake up" and start growing and multiplying. The person becomes sick and has symptoms of TB. The person will usually have a positive skin test and an abnormal chest x-ray. A culture of the person's sputum will usually grow out the TB germ (M.tuberculosis). A person with active TB disease can spread the germs to other people if special medication isn't taken. TB can be cured with proper medication and treatment. A contact investigation is done to identify, evaluate and treat anyone who might have been exposed to a person with active TB disease in order to prevent the spread of TB.

Active TB disease is usually treated with at least 4 medications (Isoniazid, Rifampin, Pyrazinamide, and Ethambutol) for at least 6 months. These medications are taken orally in the presence of a person who documents each dose taken (directly observed therapy). This ensures that every dose is taken and helps to prevent multi-drug resistant strains of TB. Multi-drug resistant TB must be treated with other drugs that are not as effective, may require injection or intravenous administration and require treatment length to be extended to two years or longer.

Directly Observed Therapy (DOT)

Bacille Calmette-Guerin (BCG) Vaccine