Self-Study Modules on Tuberculosis
This is an archived document. The links are no longer being updated.
3: Diagnosis of Tuberculosis Infection and Disease
The Medical History
- Exposure to TB. One important part of the medical
history is asking the patient about his or her exposure
to TB. Patients should be asked whether they have spent time with
someone who has infectious TB. Some people may have been exposed
to TB in the distant past, when they were children. Others may
have been exposed more recently.
Anyone who has been exposed to TB may have TB infection. Some
people become infected with M. tuberculosis without
knowing that they were exposed to it. The risk of being exposed
to TB is higher for some occupations (for example, some health
care workers) and in some residential facilities (for example,
nursing homes or correctional facilities).
- Symptoms of TB disease. Another important part
of the medical history is checking for symptoms of
TB disease. People with TB disease may or may not have symptoms.
However, most patients with TB disease have one or more symptoms
that led them to seek medical care. Occasionally, TB is discovered
during a medical examination for an unrelated condition (for example,
when a patient is given a chest x-ray before undergoing surgery).
Usually, when patients do have symptoms, the symptoms have developed
gradually, and they have been present for weeks or even months.
Pulmonary TB disease usually causes one or more of the following
- Pain in the chest when breathing or coughing
- Coughing up sputum (phlegm from deep in the lungs) or blood
The general symptoms of TB disease (pulmonary or extrapulmonary)
- Weight loss
- Night sweats
The symptoms of extrapulmonary TB disease depend on the part
of the body that is affected by the disease. For example, TB
of the spine may cause pain in the back; TB
of the kidney may cause blood in the urine.
All of these symptoms may be caused by other diseases, but
they should prompt the clinician to suspect TB disease.
- Previous TB infection or TB disease. During
the medical history, the clinician should ask the patient whether
he or she has ever been diagnosed with or treated for
TB infection or disease.
- Patients known to have a positive skin test reaction probably
have TB infection. If they were infected within the past 2
years, they are at high risk for TB disease.
- Patients who have had TB disease before should be asked
when they had the disease and how the disease was treated.
If the regimen prescribed was inadequate or if the patient
did not follow the recommended treatment, TB may recur, and
it may be resistant to one or more of the drugs used.
- Risk factors for developing TB disease. A fourth
part of the medical history is checking for risk factors
for developing TB disease. The following conditions appear
to increase the risk that TB infection will progress to disease:
- Infection with HIV, the virus that causes
- Alcohol abuse and drug injection
- Recent TB infection (within the past 2 years)
- Chest x-ray findings suggestive of previous TB
- Diabetes mellitus
- Prolonged therapy with corticosteroids
- Immunosuppressive therapy
- Certain types of cancer (e.g., leukemia, Hodgkin's disease,
or cancer of the head and neck)
- Severe kidney disease
- Certain intestinal conditions
- Low body weight (10% or more below ideal)
Clinicians should determine whether patients have any of these
conditions. In particular, HIV infection greatly increases the
risk that TB infection will progress to TB disease.
A physical examination is an essential part of the evaluation
of any patient. It cannot confirm or rule out TB disease, but
it can provide valuable information about the patient's overall
condition and other factors that may affect how TB disease is
treated if it is diagnosed.
Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination - http://www.cdc.gov/tb
Please send comments/suggestions/requests
CDC/Division of Tuberculosis Elimination
Communications, Education, and Behavioral Studies Branch
1600 Clifton Rd., NE - Mailstop E-10, Atlanta, GA 30333