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Infectious Disease YR3 > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Common areas for TB

A
  • Asia
  • Africa
  • South America
  • Eastern Europe
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2
Q

Pathogenesis of TB

A
  • Aerosol inhalation
  • = Pulmonary infection
  • Then spreads via blood
  • Initial infection can be asymptomatic
  • Can lie dormant for many years –> latent TB
  • But can then reactivate (risk 10-15% of activation)
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3
Q

How is latent TB identified?

A
  • CXR
  • Interferon gamma (Quantiferon test or T spot)
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4
Q

What is QuantiFeron?

A
  • Assess amount of interferon gamma released by T cells when they are exposed to proteins found on mycobacterium
  • Pre-exposed cells release more interferon
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5
Q

Key points about Quantiferon

A
  • Does not differentiate between active and latent TB
  • Not used to diagnose active TB
  • Can be negative during infection (esp if immunosupressed)
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6
Q

What is T spot test?

A
  • Similar to Quantiferon
  • But just T lymphocytes are isolated instead of testing whole blood
  • If there is deficiency of lymphocytes quantiferon can be negative but T spot can be positive
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7
Q

When is screening used for TB?

A
  • Interferon gamma tests used in asymptomatic patients with these risk factors:
  • Immigrants from high prevalence countries
  • Healthcare workers
  • HIV positive patients
  • Patients starting immunosupression
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8
Q

Treatment of latent TB

A
  • 3 months of Rifampicin and Isoniazid OR
  • 6 months of Rifampicin alone
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9
Q

Risks of treatment of latent TB

A
  • Need to balance risk of reactiviation with risk of hepatotoxicity
  • Pts aged older than 35 at increased risk of hepatotoxicity
  • Current guidelines advice not treating these pts for TB unless they have other RF eg healthcare worker or HIV
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10
Q

Active TB symptoms

A
  • Non-resolving cough
  • Weight loss
  • Drenching night sweats
  • Unexplained peristent fever (low or high grade)
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11
Q

Signs of TB

A
  • Clubbing
  • Cachexia
  • Lymphadenopathy
  • Hepato/splenomegaly
  • Erythema nodosum
  • Crepitations/bronchial breathing if lung changes
  • Pericardial rub if involved
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12
Q

Investigations for TB and findings

A
  • CXR - mediastinal lymphadenopathy +/- cavitating pneumonia or pleural effusion
  • CT chest - lymphadenopathy, nodes with central necrosis, can see lesions in viscera
  • MRI head - leptomeningeal involvement
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13
Q

Samples for TB - gold standard

A
  • Culturing bacteria is current gold standard
  • Treatment should be delayed if possible until samples taken
  • Culture can take up to 6 weeks so therapy started after samples taken
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14
Q

How can we culture pulmonary TB?

A
  • Sputum culture
  • Induced sputum - after nebuliser of 7% hypertonic saline
  • Bronchoscopy +/- EBUS of pulmonary lymph nodes if sputum negative

Endobronchial US guided biopsy

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15
Q

How to culture meningeal TB?

A

Lumbar puncture for TB culture and TB PCR

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16
Q

How to sample lymph node TB?

A
  • Core biopsy of lymph node
  • Fine needle aspirate not enough
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17
Q

Pericardial TB - how do we sample?

A
  • Pericardiocentesis - but not often practical
18
Q

How to sample GI TB?

A
  • Colonoscopy and bowel biopsy
  • OR Ultrasound guided omentum biopsy
19
Q

Histology of TB

A

Caseating/necrotising granulomatous inflammation

20
Q

What can occur when starting treatment for TB?

A
  • Paradoxical reaction - as bacteria die increase in inflammation can cause worsening symptoms
  • If TB occurs in place that cannot tolerate swelling (eg meningeal, spinal, pericardial), steroids are given at start of treatment
21
Q

What should all patients with miliary TB have?

A

Lumbar puncture to exclude TB meningitis

22
Q

Symptoms og TB meningitis

A
  • Subtle at first - slight personality change and headache
  • Then more meningitic
  • Finally comatose over several weeks
  • More slower onset than viral/bacterial
23
Q

Findings of MRI and LP for TB meningitis

A
  • MRI - leptomeningeal enhancement (brighter)
  • LP - high protein, low glucose, lymphocytosis
24
Q

Why do we need to make sure TB meningitis is not present?

A
  • Paradoxical reaction to therapy can be fatal
  • Given steroids when starting treatment
  • Treatment is also longer (12 months)
25
Q

Complications of pericardial TB

A
  • Effusion
  • Tamponade
26
Q

Signs of pericardial TB

A
  • Pericardial rub
  • Kussmauls sign (increase in JVP during inspiration, in normal - usually decreases)
27
Q

Miliary TB on CXR

A

Widespread throughout patient
Also found in CNS, bone marrow, pericardium

28
Q

What should all patients with miliary TB have?

A
  • Neuroimaging - CT/MRI head +/- LP to exclude CNS involvement
  • Treatment should never be delayed while awaiting biopsies too
  • Therapy started as soon as it is determined whether or not there is CNS involvement
29
Q

MDR and non-MDR resistant TB

A
  • Consider in patients who have had incomplete TB treatment previouslt
  • Usually seen in patients from abroad
  • Treatment based on sensitivities - consultant led
  • Infection control is paramount - negative pressure rooms, staff for PPE
30
Q

Treatment for TB

A

2 months of:
* Rifampicin
* Isoniazid
* Pyrazinamide
* Ethambutol
(RIFATER drug when combined) + pyridoxine (Vitamin B)

Then 4 months of:
* Rifampicin
* Isoniazid
(RIFINAH when combined)
+ pyridoxine

31
Q

Side effects of Rifampicin

A
  • Urine/tears to turn orange
  • Drug induced hepatitis
32
Q

Side effects Isoniazid

A
  • Peripheral neuropathy
  • Colour blindness
  • Drug induced hepatitis
33
Q

Side effects Ethambutol

A
  • Optic neuropathy/reduced visual acuity
34
Q

Side effects of pyrazinamide

A

Drug induced hepatitis (biggest risk)

35
Q

Moniting before and during treatment of TB

A
  • Before - LFTs and visual acuity baseline (if using ethambutol)
  • During - LFT monitoring
36
Q

What to do if LFTs derange during treatment for TB?

A
  • Stop treatment and then gradually reintroduce once normalised
  • OR can use a liver friendly regime but treatment duration is longer (24 months)
  • Liver friendly - Amikacin, Levofloxacin, Ethambutol
37
Q

Contact tracing fot TB

A
  • Once patient diagnosed –> refer to TB nurse
  • They will perform contact traving and wil test household conatcs with CXR or Quantiferon test and will treat latent TB
  • If household conacts were going to catch TB it would be before pt was admitted so visitors are allowed - unless pt has resistant TB
38
Q

Infection control for TB - rooms and discharge

A
  • Side room if non resistant TB
  • After 2 weeks of treatment - considered non-infectious to immunocompetent individuals
  • If ward manages immunosupressed patients - pts need to be in side room until discharge (regardless of smear-ve/+ve)
  • Smear positive patients can still be discharged but need to quarantine at home until 2 weeks of treatment is complete
39
Q

Infection control - PPE

A
  • Staff do not need to wear masks/aprons unless MDR TB is suspected or they are performing aerosol generating procedure
  • Patients with smear +ve TB do need to wear a mask when leaving their room until they have completed 2 weeks of treatmet
40
Q
A

Infectious Disease YR3 (6 decks)

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