Tuberculosis

Question 1

Mycobacterium tuberculosis:

Answer 1

doesn’t gram stain

-culture takes 2-3 weeks

Question 2

TB info:

Answer 2

1/3 of world pop. is infected

*** leading cause of death in HIV pts

Question 3

TB risk factors:

Answer 3

Close contacts of persons known or suspected to have active TB
Foreign-born persons from areas where TB is common
Populations with increased incidence of latent M. tuberculosis infection or TB disease, such as homeless, IVDA, HIV patients
Residents or health care workers (HCWs) exposed to high-risk patients (hospitals, homeless shelters, prisons, nursing homes, etc)
Children < 5yo with positive TB test
People who are immunocompromised (HIV, substance abuse, diabetes, silicosis, severe kidney disease, low body weight, organ transplant recipients, head/neck cancer patients, steroid treatment, RA or Crohn’s

Question 4

TB transmission:

Answer 4

• spread via airborne droplet nuclei
• 1-3 bacilli per droplet
• remains in air for hours

Question 5

TB pathogenesis:

Answer 5

• droplet inhaled and travels to alveoli where it multiplies
• some enter bloodstream and travel to other areas such as brain
• normally contained within 2-8 weeks by body. if not it spreads

Question 6

Latent TB infection (LTBI)

Answer 6

• can stay latent or can breakdown and produce TB disease
• Latent detected via TST or interferon-gamma release assay
• LTBI pts are not infectious

Question 7

Active TB:

Answer 7

• 10% of patients
• can occur soon after infections or years later
• can spread disease
• positive cultures confirm diagnosis
• reactivation occurs within 2 years in 50% of infected pts.

Question 8

Most common site of TB:

Answer 8

• Lungs (usually infectious)
• Apices most common site of reactivation
• Caseating granulomas

Question 9

Miliary TB:

Answer 9

Bacilli can spread to all parts of body, and fatal if untreated
-Millet seed appearance on CXR

Question 10

CNS TB:

Answer 10

-usually occurs as meningitis, but can occur in brain or spine

Question 11

GHON complex

Answer 11

• radiodense area on CXR
• stable granuloma
• found in 20% of LTBI

Question 12

extra pulmonary TB:

Answer 12

usually not infectious, unless person has
Concomitant pulmonary disease,
Extrapulmonary disease in the oral cavity or larynx, or
Extrapulmonary disease with open site, especially with aerosolized fluid.

Question 13

who should be tested:

Answer 13

Contacts of persons known or suspected to have infectious TB disease
People who have come to the United States within the last 5 years from areas of the world where TB is common (ex: Asia, Africa, Eastern Europe, Latin America, and Russia)
Persons who visit areas of the world where TB is common
People who live or work in congregate settings whose clients are at increased risk for TB disease
Health care workers who serve clients who are at increased risk for TB disease
Populations defined as high risk for LTBI or active TB disease, such as medically underserved, low-income persons, or persons who abuse drugs or alcohol
Infants, children, and adolescents exposed to adults at increased risk for infection or disease

Question 14

testing methods for TB infection in US:

Answer 14

Mantoux tuberculin skin test (TST)
Interferon Gamma Release Assays (IGRAs):
QuantiFERON-TB Gold In-Tube (QFT-GIT)®, and
T-Spot.TB®

Question 15

administering TST:

Answer 15

Inject 0.1 ml of PPD (5 tuberculin units) into forearm at 5 – 15 degree angle between skin layers 
Produce wheal (raised area) 6–10 mm in diameter
Follow universal precautions for infection control

Question 16

Reading TST:

Answer 16

Trained health care worker assesses reaction 48–72 hours after injection
Palpate injection site to find raised area
Measure diameter of induration across forearm; only measure induration, not redness
Record size of induration in millimeters; record “0” if no induration found

Question 17

≥5 mm induration is classified as positive in

Answer 17

HIV-infected persons
Recent contacts of infectious TB
Persons with fibrotic changes on chest radiograph consistent with prior TB
Patients with organ transplants and other immunosuppressed patients

Question 18

≥10 mm induration is classified as positive in

Answer 18

Recent arrivals from high-prevalence countries
Injection drug users
Residents and employees of high-risk congregate settings
Mycobacteriology laboratory personnel
Persons with conditions that increase risk for progressing to TB
Children <5 years of age, or children and youth exposed to adults at high risk

Question 19

≥15 mm is classified as positive in

Answer 19

Persons with no known risk factors for TB

Question 20

Interferon Gamma Release Assays (IGRAs)

Answer 20

IGRAs detect M. tb infection by measuring immune response in blood
Cannot differentiate between TB and LTBI
other tests needed
May be used for surveillance/screening, or to find those who will benefit from treatment
FDA-approved IGRAs are QFT Gold In-Tube and T- Spot.TB test

Question 21

Evaluation of Persons with Positive TB Tests

Answer 21

Facilities should consult with local health department before starting testing program to ensure evaluation and treatment resources are available
Persons with positive test should be evaluated for disease
If disease is ruled out, consider for LTBI treatment
If patient not willing or able to take treatment, educate on TB signs and symptoms

Question 22

BCG Vaccination:

Answer 22

Vaccine made from live, attenuated (weakened) strain of M. bovis
Early version first given to humans in 1921
Many TB-prevalent countries vaccinate infants to prevent severe TB disease
BCG not generally recommended in the U.S.
Use BCG only after consultation with local health department and TB experts

Question 23

Interpretation of TB Test Results in BCG-Vaccinated Persons

Answer 23

TST or IGRA not contraindicated for BCG-vaccinated persons
Results used to support or exclude diagnosis of infection
In BCG-vaccinated, interpret TST with same criteria used for non BCG vaccinated

Question 24

Who should be evaluated for TB?

Answer 24

Cough lasting more than 3 weeks
Unexplained wt loss
Hemoptysis

Additional symptoms: fever, chills, night sweats

Question 25

Medical Evaluation for TB 

Answer 25

``` Medical history Physical examination Test for TB infection Chest radiograph Bacteriologic examination ```

Question 26

Medical Hx:

Answer 26

Symptoms of disease; how long History of TB exposure, infection, or disease Past TB treatment Demographic risk factors for TB Medical conditions that increase risk for TB disease

Question 27

Symptoms of pulmonary TB:

Answer 27

``` Prolonged productive cough (3 weeks or longer) Hemoptysis Loss of appetite Unexplained weight loss Night sweats, fever Fatigue Chest pain ```

Question 28

Symptoms of possible extrapulmonary TB:

Answer 28

``` Blood in the urine (TB of the kidney) Headache/confusion (TB meningitis) Back pain (TB of the spine) Hoarseness (TB of the larynx) Loss of appetite, unexplained weight loss Night sweats, fever Fatigue ```

Question 29

Physical Examination of TB:

Answer 29

Provides valuable information about the patient’s overall condition Cannot be used to confirm or rule out TB disease May have dullness to percussion, rales, increased vocal fremitus

Question 30

CBC with TB:

Answer 30

elevated WBC

Question 31

CXR with TB:

Answer 31

Chest abnormalities suggest, but do not confirm, TB disease Posterior-anterior view is standard Apical/posterior areas of upper lobe or superior areas of lower lobe often show patchy or nodular infiltrates May see cavitation with air-fluid levels as infection progresses In immunosuppressed (e.g., HIV infected), lesions may have atypical appearance Less likely to have + TST or fever

Question 32

HIV pts pulmonary TB may have atypical radiograph:

Answer 32

Less common: cavitary disease (with higher CD4 counts) More common: infiltrates, adenopathy, or normal radiograph (with lower CD4 counts) With signs/symptoms, negative radiograph does not rule out disease With no signs/symptoms and positive TB test, negative radiograph may rule out TB in HIV-negative person

Question 33

Testing/ specimens:

Answer 33

``` Specimen collection AFB smear classification NAA testing Culture and identification Drug-susceptibility testing ```

Question 34

Specimen collection, processing, and review

Answer 34

All persons suspected of TB disease should have sputum cultured Collect at least 3 sputum specimens at 8- to 24-hour intervals, at least 1 in the morning Follow infection control precautions during specimen collection Collection methods include coughing, sputum induction, bronchoscopy, gastric aspiration

Question 35

First evidence of mycobacteria in testing come from:

Answer 35

detecting AFB in smears - results in 24 - provides preliminary presumptive diagnosis of TB

Question 36

Nucleic Acid Amiplification testing in TB:

Answer 36

NAA tests rapidly identify a specimen via DNA and RNA amplification Benefits may include Earlier lab confirmation of TB disease Earlier respiratory isolation and treatment initiation Improved patient outcomes; interruption of transmission Perform at least 1 NAA test on each pulmonary TB suspect A single negative NAA test does not exclude TB

Question 37

*Gold Standard for confirming TB:

Answer 37

Culture - culture all specimens even if smear or NAA is negative - 4-14 days - culture monthly until 2 consecutive negative cultures

Question 38

Drug-susceptibility testing:

Answer 38

Conduct drug-susceptibility testing on initial M. tb isolate Promptly forward results to the health department Repeat for patients who Do not respond to therapy or Have positive cultures despite 3 months of therapy

Question 39

New TB test: XPERT MTB/RIF Assay:

Answer 39

Test detects M. tb complex and rifampin resistance simultaneously Results in 2 hrs Sputum sample

Question 40

TB 1st Line drugs:

Answer 40

``` Isoniazid Rifampin Pyrazinamide Ethambutol Rifabutin* Rifapentine ``` * = Not approved by the U.S. Food and Drug Administration for use in the treatment of TB

Question 41

Second line TB drugs:

Answer 41

``` Streptomycin Cycloserine p-Aminosalicylic acid Ethionamide Amikacin or kanamycin* Capreomycin Levofloxacin* Moxifloxacin* Gatifloxacin* ``` *= Not approved by the U.S. Food and Drug Administration for use in the treatment of TB

Question 42

RIPE=

Answer 42

Rifampin/rifapentine Isoniazid Pyrazinamide Ethambutol