TB

Question 1

How is TB transmitted?

Answer 1

Respiratory droplets (coughing, sneezing, vocalizing) rapidly evaporate and bacilli circulate airborne

Question 2

When after initiation of treatment is the patient no longer contagious?

Answer 2

After 2 weeks of 3 or 4 drug chemotherapy or if initially was AFB +ve then after 3 negative AFBs

Question 3

In what situations is extrapulmonary TB contagious?

Answer 3

• Oral cavity lesions

Open skin lesions

Question 4

What are the 4 Dannenberg stages of pathogenesis of TB?

Answer 4

Stage 1: alveolar macrophages ingest inhaled bacillus

Stage 2: bacili replicate in macrophage and lyse it attracting more macrophages which then are infected

Stage 3: infected macrophages are activated by CD4 T helper cells and cytotoxic CD8 cells arrive. all work together to create caseating granuloma: at this point infection can progress or become latent

Stage 4: reactivation or reinfection

Question 5

List symptoms of pulmonary tuberculosis.

Answer 5

Cough	
Weight loss
Chills
Fatigue
Anorexia
Tactile fever
Chest pain
Night sweats
Dyspnea
Hemoptysis

Question 6

List 7 populations at increased risk for TB:

Answer 6

1. Foreign born in africa, asia, s. america
2. HIV
3. contacts of known case
4. medically inderserved, low income
5. long-term care facility residents
6. IVDU
7. occupational exposure
8. groups with local prevalence

Question 7

List RF for reactivation

Answer 7

HIV
Recent TB (within 2 yrs)
CXR shows prev untreated TB
IVDU
DM
silicosis
immunosuppresion (steroids, immunosuppresants)
Head/neck ca
heme dz
ESRD
intestinal bypass
chronic malabsorption
low body weight

Question 8

List 6 complications of pulmonary TB.

Answer 8

PTX
empyema
hemoptysis
pericarditis
superinfection
airway TB
endobronchial spread

Question 9

What is a Rasmussen’s aneurysm?

Answer 9

Psuedoaneurysm that results when a TB lesion or cavity that erodes into a pulmonary artery – Potential for massive (and fatal) hemoptyis

Question 10

What % of patients with active TB will have negative PPD skin testing?

Answer 10

~20%

Question 11

A normal CXR is reported to be a useful screening (high NPV) test for pulmonary TB. What is the false negative rates of a normal CXR?

Answer 11

• Immunocompetant: FN LT 1%

HIV: FN 7 – 15%

Question 12

List 4 CXR findings for TB.

Answer 12

• Upper lobe cavitary lesions
• Bilateral upper lobe infiltrates : highly likely to be TB if see on CXR!!
• Consolidation with enlarged hilar or mediastinal nodes
• Milliary TB
• Moderate to large pleural effusion
• Well circumscribed nodular coin lesions (Tuberculonmas)
• Calcified nodular scar: Gohn focus

Question 13

Provide a DDx for cavitary lesions on CXR:

Answer 13

• TB
• Other Infections:
  o Klebsiella pneumoniae
  o Staphylococcus aureus
  o M. avium complex (in HIV pts)
• Cancer:
  o Bronchogenic Carcinoma
• Other:
  o Aspiration pneumonia
  Pulmonary infarction secondary to PE

Question 14

List criteria for a positive tuberculin skin test.

Answer 14

• > 5mm: immunosuppressed, close contacts
• > 10mm: any TB RF
  15mm: all other people

Question 15

List sites of extrapulmonary TB.

Answer 15

• Lymphatic
• Pleural
• Bone or joint
• GI
• Menigeal
• Peritoneal
  Other (skin, heart, pericardium, thyroid, mastoid cells, sclera, adrenal glands

Question 16

List a differential for scrofula.

Answer 16

• Lymphoma
• Metastatic cancer
• Fungal disease
• Cat-scratch disease
• Sarcoid
• Toxoplasmosis
• Reactive adenitis
• Bacterial adenitis
• Tularemia
• Yersenia pestis

Question 17

What are the most commonly involved bone and joints in EPTB?

Answer 17

• Spine (Potts disease) from paravertebral nodes (50-70%)
• Hip, knee (15-20%)
• Other less common: ankle, elbow, wrists, shoulders

Question 18

List features of CSF in TB meningitis.

Answer 18

• WBC# 0 – 1500
• Predominance of lympohocytes (May be predominantltly PMNs)
• Increased protein
  Decreased glucose

Question 19

What is recommended treatment for TB meningititis?

Answer 19

• 4 drug regime: INH, pyrazinamide, rifampin, steroids
• Prednisone 60 – 80mg daily tapered over 4 – 6 weeks
• +/- VP shunt for hydrocephalus

Question 20

What is the most emergent presentation of TB?

Answer 20

• Massive hemoptysis = 600mL/24 hours

Question 21

List fist line TB drugs and adult and child doses.

Answer 21

First Line (RRRIPE)

• Rifampin
• Rifabutin
• Rifapentine
• Isoniazid
• Pyrazinamide
• Ethambutol

Question 22

List major side effects of the four most common TB drugs.

Answer 22

• INH
  o MOA:
  § Creates functional deficiency of pyridoxine
  § Results in GABA depletion à INH induced Sz!!
  o Toxicity:
  § Acute toxicity: refractory seizures, AGMA, coma
  § Chronic toxicity: Hepatotoxicity, peripheral neuropathy
  o Antidote:
  § Pyridoxine used in INH therapy as prevention of neuropathy
  § Acute INH induced Sz à pyridoxine 5g (70mg/kg) bolus
• RIF
  o Discolouration of body fluid
• PZA
  o Hepatotoxicy
  o Polyarthralgias
• ETH
  o Retrobulbar neuritis and colourblindness

Question 23

List risk factors for drug-resistant TB (Box-135-5).

Answer 23

· Patient
	o HIV +ve
	o Failure to respond or adhere to prior treatment
	o Unsuccessful treatment
	o Poor gastric absorption
	o Cavitary lung lesion
· Close contact with source case
· Socio-economic
	o Immigration from area with drug resistance
	o IVDU
	o Homeless
	o Imprisonment

Question 24

What are considerations when treating TB in pregnancy?

Answer 24

• TREAT! Rifampin, isoniazid, and ethambutol are NOT teratogenic.
  Give pyridoxine

Question 25

List guidelines for the management after accidental exposure to TB at work in the ED (Box-135-6):

Answer 25

• TB skin test early for baseline to assess for prior TB exposure
• Re-test in 3 months to see if there is conversion
• If Positive, check for evidence active disease CXR. If abnormal treat
• If no active disease, follow the below guidelines: