TB

Question 1

Tuberculosis (TB) Infection

Answer 1

disease caused by mycobacterium tuberculosis

Question 2

TB incidence / risk factors

Answer 2

• 1/3 population latently infected
• reactivation is cause of most active cases

Question 3

TB etiology/infectious

Answer 3

• transmission person to person via small droplets
• Long time period btwn initial infection and overt dz symptoms as a granulomatous response
  
  • Primary a pulmonary dz but you can get extrapulmonary TB too

Question 4

TB agent/basic pathophysiology

Answer 4

• mycobacterium: small, rod shaped, aerobic, non-spore forming bacilli
  
  • cell walls have high concentration of lipids/waxes
  • AFB- use Ziel Neelsen stain
  • Transmitted via aerosolized droplets (can remain in air for hours)
    
    • Bacilli need to reach alveoli to be infectious – you will have numerous bacilli in cavitary lesions
    • Alveolar macrophages engulf bacilli, replicate inside, spread via blood
  • A lto of time the host will be able to fight off the bacteria but it travels and makes homes throughout the body as granulomas develop
• At risk pts: infancy under 4, sick elderly, immunocompromised ** (aids, transplants, chemo), people who live or work in crowded areas (homeless shelters, nursing homes, prisons), alcoholism

Question 5

TB clinical presentation (signs and symptoms)


Answer 5

• 1. Atypical
     * Fever, nonproductive cough
     * Unilateral lower lobe patchy infiltrates or hilar adenopathy
• 2. Pleurisy- stabbing lung pain
     * Effusion, sometimes without focal infiltrate
     * PPD strongly positive
     * Fever, cough, pleuritic chest pain, dyspnea
     * Pleural biopsy, thoracentesis
• 3. Direct progression from primary TB to upper lobe involvement
• 4. Systemic Dissemination
     * Children
     * HIV Patients

Question 6

TB dx evaluation

Answer 6

• try to refrain/be safe when doing bronchoscopy/cough producing procedures due to spread
• DX:
• CXR for
  
  • Upper lobe fibronodular then fluffy in apices
  • The lesions coalesce, then cavitate, then have central necrosis
  • Lower lobe disease is seen in less than 15% of HIV negative adults
  • May have normal CXR
  • Hilar lymphadenopathy common
• Sputum culture- ALWAYS do to get sensitives and check for resistance (can use saline if needed)
  
  • GOLD STANDARD IS CULTURES ~~ 3-6 wks long
• AFB with radiologic and clinical correlation to make dx highly TB- 3 AFBs needed (1 every day for 3)
  
  • Need 3 negatives to be negative

Question 7

TB management plan

Answer 7

• prevention:
  
  • medication via Directly observed therapy (someone has to watch you take meds)
  • Isolation
  • Surgical mask
  • Negative pressure room- HEPA filter
  • UV Germicidal Irradiation

Question 8

TB complications

Answer 8

• Hemoptysis
• Massive hemoptysis rare
• Spontaneous Pneumothorax
• Less common
• Bronchiectasis
• Extensive pulmonary destruction
• Venous Thromboembolism
• Hypercoaguable state
• Increased risk of malignancy
• Chronic pulmonary aspergillosis

Question 9

granuloma

Answer 9

mass of granulation tissue, typically produced in response to inflammation, infection or presence of foreign substance

Question 10

granulomatous

Answer 10

immunodeficiency disease that inc body’s susceptibility to infections..

Question 11

Primary TB

Answer 11

initial infection which rarely causes significant symptoms (dormancy)

Question 12

active pulmonary infection

Answer 12

• constitutional symptoms paired with history for risk factors
  
  • fever, night sweats, wt loss*, malaise, fatigue, CP, dyspnea
• LRTI symptoms: cough/hemoptysis
  
  • Or fever alone for weeks
• Duration: longer than 3 weeks
• This can be reactivation dz
  
  • Reactivation: shows as apical posterior segments involved on CXR
• Dx: PPD/TST, sputum sample and TB culture then IGRAs

Question 13

latent pulmonary TB

Answer 13

• >=10 with medical conditions which make the patient at high risk (anti-TNF agents for RA, etc.)
• Younger than 35 and at high risk with >=10mm
• Foreign born from a high prevalence country
• Medically underserved, low income populations, black, Hispanic and native Americans
• Prison, nursing home and mental institution residents

Question 14

extra-pulmonary TB

Answer 14

• bacilli are more rare with this
  
  • pleural effusions show exudate with low glucose, high lymphocytes, but rarely has positive AFB
  • Can be hypersensitivity rxn or direct spread
    
    • After lungs, you find it MC in Lymph nodes (posterior cervical and supraclavicular)
• Can cause:
  
  • In Gu, pyuria, endometriosis, blood in urine
  • In bones, TB can be in your vertebral column called Pott’s Disease
  • In GI: find in terminal ileum/cecum
  • In CNS: subacute, basilar or hydrocephalus ; tx w/steroids
  • In heat: pericarditis

Question 15

Military TB

Answer 15

• widespread dissemination with tiny lesions …. “millet seeds”
  
  • Common in: lungs, liver, spleen, bones, joints
  • Can be primary or reactivation
  • Can present as acute or subacute
  • Same tx as pulmonary TB but longer

Question 16

TB DDx

Answer 16

• Community acquired pneumonia
• MAI
• Lung abscess (staph aureus, strep. Pneumoniae)
• Lung cancer
• Sarcoidosis
• Wegner’s granulomatosis

Question 17

PPD test

Answer 17

PPD= Purified Protein Derivative = TST = Tuberculin skin test

• Delayed hypersensitivity reaction that is associated with development of TB rxn
  
  • You measure INDURATION after 48-96 hours of intradermal injection of protein antigens
  • Skin test reactivity occurs 4-6 wks after infection
    
    • 20% of adults with active TB do not respond to PPD— false-positive in those with BCG vaccine or negative in immunocompromised pts

Question 18

Who gets PPD?

Answer 18

• Over 65
• reactivation risk
• mmunocompromised
• nursing home pts
• yearly healthcare workers

Question 19

How is PPD delivered?

Answer 19

• 0.1 mL injected intradermally; no band aid applied
• Read 48-72 hrs later
• Measure induration (palpable, raised area) NOT erythema

Question 20

Define “positive” PPD in light of the patient population being tested

Answer 20

• 5 mm- positive in pts w/ : HIV, recent TB contacts, nodular/fibrotic changes on CXR, organ/chemo pts
• 10 mm- positive in pts w/: recent immigration (5 yrs), IVDA, high risk employees (prison/hospitals/homeless), lab personnel, comorbids, children < or high risk adults
• 15 mm: ppl w/o risk factors

Question 21

Discuss the role of interferon gamma release assay (IGRA) testing in screening and diagnosis of TB

Answer 21

• Positive PPD would raise concern for latent infection at least
  
  • CXR is indicated at this point
  • Tx depends on pt history
  • Important false poistives: BCG and nontuberculous mycobacterium (MAC)

• IGRA’s- interferon gamma release assay = Quantiferon-GOLD or T SPOT.m… $$$$$
  
  • Blood test but it cannot differ between latent or active dz
  • Antigens derived from TB mix with pt’s WBC which release interferon gamma – 24 hours for results

Question 22

latent pulmonary/ active pulmonary TB tx

Answer 22

• Admit if: hypoxic or dyspneic
• All staff need N95 and droplet isolation protocol
  
  • Negative pressure room
• Standard in US: DOT (direct observed therapy)
• Multidrug tx to prevent resistance… don’t give monotherapy
  
  • RIPE for 6 months
    
    • R: Rifampin
    • I: Isoniazid w/ vitamin B6
    • P: Pyrazinamdie- for 1^st 2 months
    • E: Ethambutol – for 1^st 2 months
  • AE:
    
    • Hepatotoxicity (RIF, INH, PZA) – need LFTs and hepatitis panel
    • EMB: visual acuity baseline testing needed (ocular toxicity)
    • All can cause rash- stop all drugs at one and resume one at time
    • Drug Fever: same as rash
• For active TB: you need sputum cultures at 2 months to show its working
  
  • If positive, treat for 9 months
• Latent TB: 9 months of isoniazid is preferred due to bactericidal
  
  • Or 4m onths of RIF
  • Do not give RIF aloen to HIV pts due to resistance potential
  • Who to treat for latent?
    
    • HIV with >=5mm
    • Close contacts of newly diagnosed infectious tb >=5, and children under 4 who have been exposed
    • Recent converters – whose never been positive b4 but 10 yrs later gets positive PPD
    • People with >=5mm and abnormal CXR indicating old infection (fibrotic changes)
    • IV drug users >=10mm
    • >=10 with medical conditions which make the patient at high risk (anti-TNF agents for RA, etc.)
    • Younger than 35 and at high risk with >=10mm
      
      • Foreign born, medically underserved, prison, nursing home, mental institution

Question 23

the role of Bacillus Calmette Guerin (BCG) vaccination in other countries and how it may affect PPD interpretation

Answer 23

Those who get a BCG will ALWAYS have a positive PPD indicating a false positive. It is not worth it to get a PPD on these patients. It is administered in other countries due to the high prevalence of TB to prevent childhood TB and military TB. Not recommended in US.

• You can do a TSPOT on pts with BCG- will not produce false positive