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PR3124 Finals > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

How is M. tuberculosis transmitted?

A

Airborne transmission
Enters lower airways
- No infection if consumed by macrophage
- Cellular immunity triggered by replication in lungs -> asymptomatic (latent) or symptomatic (active)

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2
Q

What are the risk factors for latent and active TB?

A

Latent and active:

  1. Residents of prisons, homeless shelters, nursing homes
  2. Close contact with pulmonary tuberculosis patients
  3. Co-infection with HIV
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3
Q

What are the risk factors for active TB only?

A
  • Children <2y
  • Elderly >65y
  • Malnutrition
  • Immunosuppression
  • Co-infection with HIV
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4
Q

List 6 signs and symptoms for pulmonary tuberculosis.

A
  1. Productive cough
  2. Hemoptysis: cough blood
  3. Fever
  4. Fatigue
  5. Night sweats
  6. Weight loss
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5
Q

How can TB be differentiated from pneumonia?

A

Duration of symptoms
TB: gradual onset over weeks to months
Pneumonia: acute onset over hours to days

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6
Q

What are some radiological findings that assist in diagnosing TB?

A

Infiltrates in apical region (obligate anaerobe)

Cavitary lesions

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7
Q

Indications for latent TB infection (LTBI) screening

A

High risk + intent to treat if positive

  • Children with recent TB contact
  • HIV-infected individuals
  • Considered for tumor necrosis factor antagonist therapy (immunosuppressive therapy)
  • Transplant patients
  • Dialysis (frequent healthcare encounters)
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8
Q

Tests for LTBI

A

Test if there is past exposure to TB

  1. Tuberculin skin test (tuberculin purified protein derivative test)
    - inject 0.1ml of PPD intradermally -> read after 48-72h by trained reader -> read diameter of induration not redness
    - positive is >10mm since most SG people have received BCG
  2. Interferon-gamma release assay
    - blood collection into special tubes -> measure interferon-gamma released by WBC in response to incubation with M. tuberculosis specific antigens
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9
Q

What are the advantages and limitations of tuberculin skin test and interferon-gamma release assay?

A
  1. Tuberculin
    (+) Low cost, no need for blood samples
    (-) false negative (immunosuppressed), false positive (environmental contact, BCG vaccination), intra-reader variability
  2. Interferon-gamma
    (+) no false positive in BCG-vaccination, minimal cross-reactivity with non TB mycobacterium, few hours
    (-) false negative (immunosuppressed), cost, blood samples
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10
Q

Diagnosis of active TB

A

Clinical suspicion:
- History
- Risk factors (Immune status (HIV, diabetes), cramped living conditions, nutritional status, age, travel history)
- Clinical presentation
- Physical exam findings
- Chest X ray findings
Initiate treatment if sputum obtained for Ziehl Neelsen stain for acid fast bacilli (AFB) is positive

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11
Q

What are some infection control considerations for active TB patients?

A

Hospitals: airborne precautions
- negative pressure room & PPE
- Stop airborne precautions after 2 weeks of effective treatment
Community: take TB medications, practice cough etiquette, ventilate home
- No need to avoid household members (low risk of transmission on effective treatment)

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12
Q

Benefits & considerations for treating LTBI

A

Reduce lifetime risk of progression to active TB to 1%
Monotherapy is sufficient
Prior to initiation:
- exclude active TB
- weigh risk vs benefit (side fx for underlying liver disease -> choose not to treat LTBI)

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13
Q

Treatment of LTBI

A
  1. PO isoniazid 5mg/kg OD (max 300mg)
    - x6mo or 9mo (HIV)
    - Preferred in pregnancy, lactation, HIV
    - Coadminister with pyridoxine (>10mg/d) to minimise neuropathy
  2. PO rifampicin 10mg/kg OD (max 600mg)
    - x4 mo
    - Alternative if cannot tolerate isoniazid
  3. PO isoniazid + rifapentine 900mg weekly
    - 12 weeks (not recommended for HIV)
    - given under DOT (directly observed therapy)
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14
Q

Who keeps track of TB in Singapore?

A

National Tuberculosis Registry: mandatory reporting by healthcare professionals
Singapore TB Elimination Programme (STEP):
- Promote DOT (compliance, best treatment outcomes)
- National Treatment Surveillance Registry
- Contact investigations (LTBI and treatment)

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15
Q

What are the benefits of treating active TB?

A 
Patient:
- reduce number of replicating and persisting bacteria
- durable cure and prevent relapse
- prevent resistance
Public health: minimise transmission
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16
Q

What tests can be used to confirm diagnosis of active TB?

A

Culture: gold standard

  • For confirmation of TB: 4-8wk
  • For drug susceptibility tests: 4-6 wk
17
Q

What are the 6-month and 9-month treatment schedules?

A

6-month:
- intensive phase (2mo): daily RIF + INH + PZA + EMB/STM
- continuation phase (4mo): daily or 3x/week RIF + INH
9-month (unlikely to tolerate PZA - elderly, liver disease):
- intensive phase (2mo): daily RIF + INH + EMB
- continuation phase (7mo): daily or 3x/week RIF + INH
* only switch to continuation phase after confirmed susceptibility to RIF and INH OR culture negative pulmonary TB

18
Q

What are the doses of RIF and INH for the continuation phase?

A

PO rifampicin 10mg/kg 3x/week, max 600mg
- 100mg, 300mg tabs
PO isoniazid 15mg/kg 3x/week, max 900mg
- 150mg, 300mg tabs

19
Q

1st line treatment for active TB

A 
All OD at same time: concentration-dependent killing
PO rifampicin 10mg/kg OD, max 600mg
- 100mg, 300mg tabs
PO isoniazid 5mg/kg OD, max 300mg
- 150mg, 300mg tabs
PO pyrazinamide 15-30mg/kg OD, max 2g
- 500mg tabs
PO ethambutol 15-25mg/kg OD, max 1600mg
- 100mg, 400mg tabs
IM streptomycin 10-15mg/kg OD, max 1g
- 1g vial
20
Q

Which 1st line anti-TB drugs require renal dosage adjustment?

A

Pyrazinamide
Ethambutol
Streptomycin

21
Q

DDIs with TB medications

A

INH inhibits CYP2C19, 3A4, 2D6, 2E1

RIF induces CYP1A2, 2C9, 2C19, 3A4, pgp

22
Q

How can we resolve nausea and vomiting during DOT?

A

take rifampicin & isoniazid earlier

pyrazinamide, ethambutol, pyridoxine later

23
Q

What are the risk factors for hepatotoxicity in TB treatment?

A 
Drugs: RIF, INH, PZA
Risk factors: 
- age >35 y
- female
- underlying liver disease
- concurrent alcohol use 
- HIV
24
Q

How can we educate patients on hepatotoxicity for both latent and active TB treatment?

A

Symptoms: nausea, vomiting, unexplained fatigue, abdominal discomfort/pain
Stop treatment and see a doctor immediately if you experience any symptoms

25
Q

Monitoring for LFTs

A

No risk factor: only monitor LFT if there are symptoms of hepatotoxicity (during treatment)
>1 risk factor: check baseline LFT before treatment
- check LFT every 2-4 weeks during treatment
Hepatotoxicity: ALT > 3x upper limit of normal [ULN] with symptoms; OR ALT > 5x ULN without symptoms

26
Q

How should we manage treatment if there is hepatotoxicity?

A
  • Stop treatment & monitor LFT 1-2x a week
  • LBTI: re-challenge INH when ALT <2x ULN otherwise switch to RIF x4mo (if can’t tolerate INH)
  • Active TB: re-challenge sequentially when LFT normalise + symptoms resolve (RIF, INH etc) -> failure req non-hepatotoxic regimen (EMB + FQ + STM)
27
Q

Monitoring for visual acuity

A

Rationale: EMB causes visual toxicity (reduce visual acuity + red-green color discrimination)
Monitor visual acuity + color discrimination tests:
- Baseline for all patients
- Monthly: taking EMB >2mo or renal insufficiency (CKD)
Educate patient to stop treatment and see doctor immediately if they experience vision changes

PR3124 Finals (5 decks)

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