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15 Cards in this Set

  • Front
  • Back
What causes TB?
TB is an infection caused by a slow growing aerobic bacillus.

Mycobacterium tuberculosis, which is not decolorized by acid alcohol, and thus is an "acid fast bacillus".
What are the risk factors for tuberculosis?
MAJOR risk factors for TB infection:

1. close contact with smear-positive patient
2. HIV infection
3. Homelessness
5. Institutionalization (prision)
6. Prior residence in endemic area (Africa, SE asia, Central America)

MINOR risk factors for TB infection:

1. Diabetes mellitus
2. Gastrectomy
3. Silicosis
Who is at risk for multidrug-resistant TB?
Most multidrug-resistant TB in the US has occurred in those in institutions such as prisons and nursing homes, and in HIV-infected individuals.
What is the purpose of PPD screening?
PPD screening identifies patients who have been exposed to TB.
A small sample of purified protein derivative is placed under the skin and incites an inflammatory reaction if the patient already has immune response against TB. What does this indicate?
This indicates exposure. As well as active infection, a positive PPD result also suggests dormant, live bacteria are present as latent infection, waiting for a time of immunosuppression to cause reactivation TB.

PPD interpretation depends on the host characteristics and diameter of induration present.
T or F: Once a patient has a known positive PPD reaction, never retest, as subsequent reactions may cause painful inflammation and skin necrosis.
My patient's screening PPD is positive. What should I do next?
Rule out active infection because treatment of active infection requires multidrug therapy, whereas exposure with latent infection can be treated with INH alone in most cases.
What should I focus on in the history and physical if a patient has a postive PPD?
Ask about constitutional, pulmonary, GI and GU symptoms, as well as about joint pains.

Perform full exam and get a CXR.

Any signs or symptoms that could represent active pulmonary or nonpulmonary TB infection require further work-up.
Interpreting induration reaction to PPD Testing.

Reaction: less than 5mm
Negative for all patients
Interpreting induration reaction to PPD Testing.

Reaction: 5mm or greater
Positive for the following patient populations:

1. HIV infected patients
2. Organ transplant patients
3. Patients on chronic prednisone
4. Recent contacts with TB-infected patients
4. X-ray findings suggesting prior TB infection
Interpreting induration reaction to PPD Testing.

Reaction: 10mm or greater
Positive for the following patient populations:

1. Children under 4
2. Children exposed to high risk adults
3. IVDU without HIV infection
4. Patients with gastrectomy, malignancy, diabetes, silicosis, renal insufficiency
5. Recent immigrants from country with high prevalence of TB
6. Staff from AFB lab
7. Staff from prisons, nursing homes, hospitals, shelters
Interpreting induration reaction to PPD Testing.

Reaction: 15mm or greater
Positive for all patients, including those with no known risk factors for TB.
What are the typical symptoms of active TB infection?
Classic symptoms are fever, night sweats, weight loss, and cough productive of thick sputum. Hemoptysis and dyspnea are symptoms of advanced disease.

In elderly and HIV-infected patients, symptoms may be more subtle (anorexia, fatigue, confusion, weakness).
When should I think of TB in the differential diagnosis?
Patients who present with typical symptoms and major risk factors should have a work-up for TB.

Anyone with an upper lobe infiltrate on CXR should also be considered for a work-up.

Think of TB, especially reactivation TB, in elderly patients who have infiltrates on CXR that do not respond to standard antibiotic therapy.

Alcoholics are at higher risk for TB due to a higher likelihood of homelessness or incarceration.
What is the work-up for TB?
Order a CXR

If infiltrates are present, especially in the upper lobe, obtain 3 separate morning sputum samples for AFB smear and culture.

Patients admitted to the hospital and undergoing TB work-up should be kept in respiratory isolation until 3 smears are negative.