Tuberculosis test (or PPD) is performed with an
Tuberculosis (TB) is an infectious disease caused by a germ (bacterium) called
Mycobacterium tuberculosis. This germ primarily affects the lungs and may infect
anyone at any age.
In the United States, the number of TB cases steadily decreased until 1986 when
an increase was noted; TB has continued to rise since. Today, ten million
individuals are infected in the U.S., as evidenced by positive skin tests, with
approximately 26,000 new cases of active disease each year. The increase in TB
cases is related to HIV/AIDS, homelessness, drug abuse and immigration of
persons with active infections.
How is TB Contracted?
TB is a contagious or infectious disease that is spread from person-to- person.
A person is usually infected by inhaling the germs which have been sprayed into
the air by someone with the active disease who coughs.
However, inhaling the germ does not usually mean you will develop active disease.
A person’s natural body defenses are usually able to control the infection so
that it does not cause disease. In this case, the person would be infected, but
not have active disease. Only about 10% of those infected will actually develop
TB in their lifetimes.
Active disease can occur in an infected person when the body’s resistance is low
or if there is a large or prolonged exposure to the germs that overcome the
body’s natural defenses. The body’s response to active TB infection produces
inflammation which can eventually damage the lungs. The amount of damage may be
quite extensive, yet the symptoms may be minimal. The usual symptoms of disease
due to TB are:
-Fever -Night sweats -Cough -Loss of appetite -Weight Loss -Blood in the sputum
(phlegm) -Loss of energy
To diagnose TB, your clinician will gather five important pieces of information:
-Symptoms -History of possible exposure and onset of symptoms -Tuberculin skin
test or PPD -Chest X-ray Sputum test
Tuberculin Skin Test
The tuberculin skin test (or PPD) is performed with an extract of killed
tuberculosis germs that is injected into the skin. If a person has been infected
with tuberculosis, a lump will form at the site of the injection–this is a
positive test. This generally means that TB germs have infected the body. It
does not usually mean the person has active disease. People with positive skin
tests but without active disease cannot transmit the infection to others.
If a person has been infected with TB, but active disease has not developed, the
chest X-ray usually will be normal. Most people with a positive PPD have normal
chest X-rays and continue to be healthy. For such persons, preventive drug
therapy may be recommended.
However, if the germ has attacked and caused inflammation in the lungs, an
abnormal shadow is usually visible on the chest X-rays. For these persons,
aggressive diagnostic studies (sputum tests) and treatment usually are
Samples of sputum coughed up from the lungs can be tested to see if TB germs are
present. The sputum is examined under a microscope (a “sputum smear”) to look
for evidence of the presence of TB organisms. The organisms are then grown in
the laboratory to identify them as TB germs and to determine what medications
are effective in treating them. These studies are referred to as culture and
susceptibility testing. State health department laboratories and reference
laboratories can perform such testing.
Treatment of TB
Individuals with a positive tuberculin skin test may or may not receive
preventive drug therapy depending on the exposure history, the timing of the
skin test conversion (when the test changes from negative to positive) and other
factors in the individual’s medical history. When it is known that a person has
recently been in close contact with an individual with active tuberculosis and
has developed a positive tuberculin skin test, preventive treatment is advisable
due to a relatively high risk of developing active disease. Isoniazid (INH) may
be prescribed for six to nine months as preventive treatment and for twelve
months in persons who are HIV positive.
Since the advent of anti-tuberculosis drugs in the 1940s, the treatment of drug
susceptible tuberculosis has become highly effective if administered and taken
properly. Treatment no longer requires prolonged hospital stays. In many cases,
a patient with a new case of TB can be treated at home. Others will enter the
hospital to be placed on a medication program and to be isolated until the
disease is controlled. When the person is no longer infectious, he or she can
leave the hospital and continue on medication at home. Hospitalization in such
cases may be a few weeks to several months depending on the severity of the
disease and the effectiveness of the treatment program.
In most cases, a treatment program for drug-susceptible TB involves taking two
or four drugs for a period of time ranging from six to nine months. Medications
may include isoniazid, rifampin, pyrazinamide, ethambutol or streptomycin. It is
necessary to take multiple drugs and to take all of the doses prescribed,
because all of the TB germs cannot be destroyed by one drug.
It is important to realize that hospitalization for a TB patient, when necessary,
represents only the beginning of treatment. Since active TB is slow to respond
completely to therapy, medications prescribed by a clinician must be taken
faithfully for a long period of time (at least 6 months, in some cases for a
year or more). If the TB medications are not taken regularly, serious
complications may develop:
-the organisms may become resistant to one or more of the drugs, -there may be
an increased risk of toxic reactions from the drugs and -there is a high risk of
disease relapse or recurrence.
Given the many effective medications available today, the chances are excellent
that tuberculosis in an individual can be cured. It is important, however, for
the patient to understand the disease and to cooperate fully in the therapy
In a small percentage of cases, the initial treatment does not go as planned. It
may be that the patient is not taking the medications regularly, the medication
program is not sufficient for a particular infection or the medications are not
absorbed properly. In these patients, there is a tendency for the germs to
become resistant to some or all of the drugs. Sometimes a person has initial
drug-resistant disease. In other words, the TB germs they contracted were from a
person with drug-resistant TB.
Drug-resistant TB is very difficult to treat and requires more and different
medications for a longer period of treatment. Sometimes, surgery is needed to
remove areas of destroyed lung that contain many millions of germs that are
inaccessible to antibiotics. A person with drug-resistant TB should be treated
by a specialist with considerable experience in managing the disease and this
treatment should be initiated in a hospital setting.
TB and National Jewish
Since 1899, the National Jewish Center for Immunology and Respiratory Medicine
in Denver has treated tuberculosis patients. The hospital was established to
care for the thousands of persons who flocked to Colorado’s high altitude and
dry climate, seeking the elusive cure for their tuberculosis.
In 1919, a research department was established at the hospital. When anti-TB
drugs became available in the late 1940s, National Jewish was one of the first
institutions to base its TB treatment program on the new chemotherapy,
contributing refinements and developing combinations of drugs to overcome the
problems of drug toxicity and resistance.
Today, National Jewish is one of the world’s leading centers for the diagnosis
and treatment of tuberculosis. Research continues at the Center to define new
approaches to treat difficult TB infections. Our world renowned doctors are
backed by state-of-the-art laboratories that help them select the most effective
drug combinations and dosages. For drug-resistant TB, the New York Times
recently wrote that National Jewish provides “the most sophisticated and
aggressive treatment the world has to offer.” National Jewish offers a
comprehensive evaluation for TB and drug-resistant TB. It is important to have a
referral from the doctor along with previous medical records, chest X-rays and
recent TB drug susceptibility testing before scheduling a TB evaluation at the
Center. In most cases doctors refer a patient for our highly specialized in-
patient program. To refer a patient for a TB evaluation, a doctor can call 303-
398-1279. In addition, doctors and other health-care professionals can use this
number to obtain consultations regarding current diagnosis and treatment
information. Consultation is available for health-care professionals only.