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finals 3124 > TB > Flashcards

TB Flashcards

1
Q

pathophysiology of TB

A

98% transmission via airborne

  • consumed by macrophages
  • replicates in lungs causing cellular immunity
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2
Q

latent and active TB risk factors

A
  1. residents of prison, homeless shelter, nursing homes
  2. close contact with pulmonary tuberculosis patients
  3. co-infection with HIV
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3
Q

Active TB risk factor

A
  1. children <2yo
  2. elderly >65yo
  3. malnutrition
  4. immunosuppression
  5. co-infection with HIV
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4
Q

Clinical presentation of TB

A
  • primarily a pulmonary infection

- extra- pulmonary TB possible: in the bone & joint, spine, CNS

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5
Q

signs and symptoms of TB

A
  1. productive cough
  2. hemoptysis
  3. fever
  4. fatigue
  5. night sweats
  6. weight loss
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6
Q

radiological findings in TB

A
  1. infiltrate apical region

2. cavity lesions

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7
Q

how are TB symptoms different from pneumonia symptoms

A

TB: gradual onset (weeks to months)

Pneumonia: acute onset (hours to days)

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8
Q

indication for latent TB infection LTBI screening

A
  1. high risk group and

2. intent to treat if possible

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9
Q

definition of high risk Latent TB group

A
  1. children with recent TB contact
  2. HIV infected individuals
  3. pt considered for tumor necrosis factor antagonist therapy
  4. transplant pt
  5. dialysis pt
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10
Q

reasons not to treat TB

A

if patient has life limiting diseases like end stage cancer, it doesnt make sense to expose pt to more medication and toxicity

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11
Q

diagnostic test for latent TB

A
  1. tuberculin skin test (mantoux test, tuberculin purified protein derivative PPD test)
  2. interferon-gamma release assay (quantiFERON-TB- gold, T-SPOT.TB)
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12
Q

describe tuberculin skin test

A
  1. infect 0.1ml of PPD intradermally
  2. read after 48-72h by trained reader
  3. read diameter of induration (not area of redness)
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13
Q

describe interferon-gamma release assay

A
  1. blood collection into special tubes
  2. measures the interferon-gamma released by WBC in the response to incubation with M.tuberculosis- specific antigens

note: previously exposed to TB will be able to mount an immune response against the test

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14
Q

strengths of tuberculin skin test

A
  1. highly sensitive (95-98%)
  2. low cost
  3. no need to collect blood samples
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15
Q

limitation of tuberculin skin test

A
  1. false neg (immuno)
  2. false pos (environmental contact with non-TB mycobacteria, BCG vax (mostly pos >10mm)
  3. no universally accepted standard for interpreting results
  4. inter-reader variability
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16
Q

strengths of interferon-gamma release assay

A
  1. performance as good as PPD
  2. no false positive in BCG-vax
  3. minimal cross reactivity with non-TB mycobacteria
  4. results avail within few hours
17
Q

limitations of interferon-gamma release assay

A
  1. more expensive
  2. need blood samples
  3. false neg (immuno- may not mount adequate immune response)
18
Q

Active TB diagnosis

A

sputum obtained for Ziehl-Neelsen stain for acid fast bacilli AFB
- if pos, intiate tx

19
Q

infection control for active TB in hospitals

A
  • need airborne precaution
  • negative pressure rooms
  • PPE and N95 mask
20
Q

infection control for active TB in community

A
  • no need to avoid household members
  • take TB meds
  • practice cough etiquette
  • ventilate homes
21
Q

why treat LTBI

A
  • reduce lifetime risk of progression to active TB from 10% to 1&
  • reducing number of replicating and persisting bacteria
  • achieve durable cure and prevent relapse
  • prevents development of res
  • minimise transmission
22
Q

what to do before starting LTBI tx

A
  1. exclude active TB

2. weigh risk benefits

23
Q

tx of LTBI

A
  1. isoniazid: 5mg/kg PO OD (max 300mg) x 6mth (9mth if HIV)
    - co-adminster with pyridoxine (at least 10mg/d to minimise neuropathy)
  2. rifampicin: 10mg/kg PO OD (max 600mg) x 4mth
    - alternative for iso
  3. isoniazid + rifampicin: 900mg PO weekly (300+600mg) x12w
    - given under direct observed therapy
    - not suitable for HIV pt
24
Q

rifampicin first line TB dosing

A
  • PO 10mg/kg OD; max 600mg
  • PO 10mg/kg 3x/week; max 600mg
  • no renal dose adjustment
  • tablet size: 100mg, 300mg
25
Q

isoniazid first line TB dosing

A
  • PO 5mg/kg OD max 300mg
  • PO 15mg/kg 3x/week max 900mg
  • no renal dose adjustment
  • tablet size: 150mg, 300mg
26
Q

pyrazinamide first line TB dosing

A
  • PO 15-30mg/kg; max 2g
  • need renal dosage adjustment
  • tablet size: 500mg only
27
Q

ethambutol first line TB dosing

A
  • PO 15-25mg/kg OD; max 1600mg
  • need renal dosage adjustment
  • tablet size: 100mg, 400mg
28
Q

streptomycin first line TB dosing

A
  • IM 10-15mg/kg OD; max 1g
  • need renal dose adjustment
  • avail in 1g vial
29
Q

tx regimen for initial TB

A
  • OD of R+I+P+E/S x first 2mth
  • OD or 3x/week of R+I x next 4mth
  • can step down when confirmed susceptible to R&I or when neg pulmonary TB culture
30
Q

alternative tx regimen for TB

A

if pt cannot tolerate Pyrazinamide:

  • OD of R+I+E x first 2 mths
  • OD or 3x/week of R+1 x 7mth
  • can step down when confirmed susceptible to R&I or when neg pulmonary TB culture
31
Q

Who should avoid Pyrazinamide

A
  1. elderly
  2. liver failure (hepatotoxicity)
  3. kidney failure (renal toxicity)
  4. can cause gout like symptoms
32
Q

TB drugs with hepatotoxicity

A
  1. rifampicin
  2. isoniazid
  3. pyrizinamide
33
Q

symptoms of hepatotoxity

A
  1. NV
  2. unexplained fatigue
  3. abdominal pain
  4. ALT > 3x [ULN] + symptoms
  5. ALT > 5x [ULN]
34
Q

DDI of TB drugs

A
  1. Isoniazid inhibits 2C19, 2D6, 3A4, 2E1

2. Rifampicin induces 1A2, 2C9, 2C19, 3A4, PGP

35
Q

recommendation for LFT monitoring for TB

A
  1. no risk factor: no need baseline/monitor
  2. risk factor bef tx: check baseline LFT
  3. risk factor during tx: check LFT every 2-4w
36
Q

management of LTBI when hepatotoxicity

A
  1. stop tx immediately
  2. monitor LFTs
  3. re- challenge with Isoniazid when ALT improve <2x [ULN]
  4. switch to rifamipicin x4mth if pt cannot tolarate
37
Q

management of active TB when hepatotoxicity

A
  1. stop tx immediately
  2. monitor LFTs
  3. re- challenge sequentially when LFT normalised and symptoms resolved (start 1 med at a time)
  4. if rechallenge fail, may need non hepatotoxic drug regimen (eg. Ethambutol+ FQ + strep)
38
Q

ADR to look out for Ethambutol

A

visual toxicity:

  • reduced visual acuity
  • reduced red-green color discrimination
  • monthly monitoring
39
Q

risk factor for hepatotoxicity

A
  1. age >35yo
  2. females
  3. underlying liver disease
  4. concurrent alc use
  5. HIV

finals 3124 (7 decks)

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