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#passmed 2022 > TB > Flashcards

TB Flashcards

1
Q

What factors increase the likelihood of someone having TB? (6 things)

A
  1. Hx prior TB exposure / treatment
  2. Low immunity (HIV)
  3. Travel to area where TB is endemic
  4. Homelessness
  5. Jail / IV drug use
  6. Gastrectomy
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2
Q

What are the classical features of pulmonary TB? (7 things)

A
  1. Fever
  2. Night sweats
  3. Fatigue
  4. Cough
  5. Haemoptysis
  6. Chest pain
  7. Weight loss / anorexia
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3
Q

What is the bacteria that causes TB?

A

Myobacterium tuberculosis

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4
Q

When does active infection of TB occur?

A

Inadequate containment by immune system (T cells / macrophages)

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5
Q

What 2 things can active infection of TB arise from?

A
  1. Primary infection

2. Reactivation of latent disease

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6
Q

What is latent TB?

A

Infection without disease

Because contained by immune system (e.g granuloma formation prevents bacteria growth + spread)

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7
Q

What tests will show up positive / negative in latent TB?

A

Positive: skin / blood tests

Negative: Sputum / CXR

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8
Q

What are the risk factors for reactivating latent TB?

A
  1. New infection
  2. HIV
  3. Organ transplant
  4. Immunosuppression
  5. Homeless / jail
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9
Q

What are the systemic clinical features of TB? (7 things)

A
  1. Fever (low grade)
  2. Anorexia
  3. Malaise
  4. Weight loss
  5. Night sweats
  6. Erythema nodosum (red + swollen fat under skin)
  7. Clubbing (bronchiectasis)

FAM W NEC

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10
Q

What are the clinical features of PULMONARY TB? (4 things)

A
  1. Cough (dry then productive)
  2. Haemoptysis
  3. Pleurisy (inflamm pleura)
  4. Pleural Effusion
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11
Q

What are the clinical features of Tuberculus Lymphadenitis? (2 things)

A
  1. Painless enlargement of cervical / supraclavicular lymph nodes
  2. Systemic symptoms (FAM W NEC)
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12
Q

What are the nodes like in Tuberculus Lymphadenitis?

A

Firm to touch and NOT acutely inflamed

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13
Q

Does Tuberculus Lymphadenitis occur with PULMONARY TB?

A

Yes and can also occur without

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14
Q

How is Tuberculus Lymphadenitis investigated? (3 things)

A
  1. Fine needle aspiration
  2. AFB staining (sputum stain for Mycobacteria)
  3. Culture

FAC

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15
Q

What are the clinical features of GASTROINTESTINAL TB? (3 things)

A
  1. Vomiting
  2. Colicky abdominal pain
  3. Bowel obstruction (bc bowel wall thickening / stricture)
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16
Q

What is required for the diagnosis of GASTROINTESTINAL TB?

A

Biopsy

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17
Q

What distinguish GASTROINTESTINAL TB from Crohn’s disease? (2 things)

A

Caseation necrosis

Absence of transmural cracks

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18
Q

What are the clinical features of SPINAL TB? (4 things)

A
  1. Pain + bony tenderness for weeks / months
  2. Bony destruction / vertebral collapse
  3. Soft tissue abscess
  4. Slow progression
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19
Q

What is Miliary TB?

A

When haematogenous dissemination leads to formation of foci of granulomatous tissue (2mm) on lung

Potentially fatal form of TB

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20
Q

What is CNS TB?

A

Haematogenous spread leading to foci of infection in brain + spinal cord

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21
Q

What do foci of CNS TB enlarge to form?

A

Tuberculomas

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22
Q

What does foci of CNS TB rupture lead to?

A

Meningitis

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23
Q

What should you check the CSF for in CNS TB? (4 things)

A
  1. Leucocytosis
  2. Raised protein
  3. Plasma glucose <50%
  4. AFB stain, PCR & culture
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24
Q

What are the clinical features of GENITOURINARY TB? (5 things)

A
  1. Dysuria
  2. Frequency
  3. Loin pain
  4. Haematuria
  5. Sterile pyuria (WBC in urine)
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25
Q

What can granulomas in GENITOURINARY TB cause?

A
  1. Fibrosis
  2. Strictures
  3. Infertility
  4. Genital ulceration
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26
Q

What does CARDIAC TB involve?

A

Pericardium (pericarditis, pericardial effusion, constrictive pericarditis)

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27
Q

What are the diagnostic tests for latent TB? (2 things)

A
  1. Tuberculin skin testing (TST) (aka Mantoux test)

2. Interferon-gamma release assays (IGRAS)

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28
Q

What reduces sensitivity of both latent TB tests?

A

Immune suppressed states

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29
Q

What are the diagnostic tests for active TB? (4 things)

A
  1. CXR
  2. Sputum smear
  3. Sputum culture
  4. Nucleic acid amplification test (NAAT)
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30
Q

What is seen in a CXR in active TB? (4 things)

A
  1. Cavitation (mainly upper lobe if reactivated TB)
  2. Calcification
  3. Effusion (yh)
  4. Lymphadenopathy

(Caseating necrosis seen in histology)

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31
Q

How many specimens of sputum smear are needed for TB diagnosis?

A

3 specimens

Including an early morning sample

32
Q

What is the sputum smear stained for in TB diagnosis?

A

For presence of acid-fast bacteria (AFB)

33
Q

If AFB is seen on the sputum smear (in TB diagnosis), what are your next steps? (2 things)

A
  1. Start treatment

2. Isolate patient

34
Q

Why is sputum culture better than sputum smear?

A

More sensitive

35
Q

How long does sputum culture take?

A

1-3 weeks (liquid)

4-8 weeks (solid)

36
Q

What does Nucleic acid amplification test (NAAT) do in diagnosing TB?

A

Directly detects M. tuberculosis in sputum by DNA / RNA amplification

Rapid diagnosis (under 24 - 48 hours)

37
Q

How is EXTRAPULMONARY TB diagnosed?

A
  1. Investigate or coexisting pulmonary disease
  2. Obtain material from aspiration / biopsy (lymph node / pleura / bone / synovium / GI tract) for AFB staining
  3. NAAT on any sterile body fluid (CSF / pericardial fluid)
38
Q

What are the first line abx for TB treatment?

A

Rifampicin
Isoniazid
Pyrazinamide
Ethambutol

RIPE

39
Q

How does Rifampicin affect enzymes?

A

It is an Enzyme Inducer

So take care with:

  1. Warfarin
  2. Calcineurin inhibitors (immunosuppressive drugs)
  3. Oestrogens
  4. Phenytoin (seizure drug)
40
Q

What are some irrelevant side fx of Rifampicin? (2 things)

A
  1. Turns body secretions orange
    (urine / tears)
  2. Flu like symptoms
41
Q

What is an important side fx of Rifampicin?

A

Altered liver function (Hepatotoxicity)

42
Q

What are the side fx of Isoniazid? (3 things)

A
  1. Peripheral neuropathy (bc X form pyridoxine aka vit B6)
  2. Hepatoxicity - Enzyme Inhibitor / Hepatitis
  3. Agranulocytosis (low WBC)
43
Q

How is the side fx of Isoniazid overcome?

A

Give with prophylactic pyridoxine (Vit B6)

44
Q

What are the side fx of Isoniazid? (3 things)

A
  1. Peripheral neuropathy (bc X form pyridoxine aka vit B6)
  2. Hepatoxicity - Enzyme Inhibitor / Hepatitis
  3. Agranulocytosis (low WBC)
45
Q

What are the side fx of Pyrazinamide? (4 things)

A
  1. Hyperuricaemia causing gout
  2. Arthralgia (joint pain) / Myalgia (muscle pain)
  3. Hepatotoxicity
  4. Kidney problems
46
Q

When should the dose of Pyrazinamide be reduced?

A

If the eGFR is below 30

47
Q

What is the side fx of Ethambutol?

A
  1. Colour blindness
  2. Reduced visual acuity
  3. Optic neuritis
48
Q

What should be checked before and monitored during when Ethambutol is diagnosed?

A

Visual acuity

49
Q

What is the recommended dose of Rifampicin for the average adult (over 50kg)?

A

600 mg once daily for 6 months

50
Q

What is the recommended dose of Isoniazid for the average adult (over 50kg)?

A

300 mg daily for 6 months

51
Q

What is the recommended dose of Pyrazinamide for the average adult (over 50kg)?

A

2 g once daily for 2 months (initial phase).

52
Q

What is the recommended dose of Ethambutol for the average adult (over 50kg)?

A

15 mg/kg once daily for 2 months

53
Q

What is the mechanism of action of Rifampicin?

A

Inhibits bacterial DNA-dependent RNA polymerase –> prevents transcription of DNA into mRNA

54
Q

What is the mechanism of action of Isoniazid?

A

Inhibits mycolic acid synthesis

55
Q

What is the mechanism of action of Pyrazinamide?

A

It is converted by pyrazinamidase –> pyrazinoic acid which inhibits fatty acid synthase (FAS)

56
Q

What is the mechanism of action of Ethambutol?

A

Inhibits arabinosyl transferase (enzyme) which polymerizes arabinose –> arabinan

57
Q

Which patients need their Ethambutol dose adjusted?

A

Patients with renal impairment

58
Q

Where does dormant tuberculosis most frequently reactivate?

And why?

A

Lung APEX

Because most oxygenated area –> allows faster myobacteria multiplication + spreading

59
Q

What is the general pathophysiology of TB? (6 steps)

A
  1. Inhalation of Mycobacterium tuberculosis via droplet
  2. Deposition in the lung alveoli
  3. Engulfed by alveolar MACs
  4. Proliferates in MACs
  5. Release
  6. Immune response
60
Q

What (AFB) stain is used to identify myobacteria in TB diagnosis?

A

Ziehl-Neelsen stain

61
Q

What is the histological finding in patients with granulomas resulting from a TB infection?

A

Epithelioid histiocytes

62
Q

Why is an AFB smear alone insufficient in achieving a definitive diagnosis for TB?

A

AFB smear is not specific for TB - all mycobacteria will stain positive

63
Q

What is the order of sensitivity of active TB diagnostic methods?

A

Culture (most sensitive)
NAAT
Smear

64
Q

What is the histological pathophysiology of TB? (3 steps)

A
  1. MAC migrate to regional lymph nodes.
    The lung lesion + affected lymph nodes = Ghon Complex
  2. Leads to formation of granuloma (collection of epithelioid histiocytes)
    There is caseous necrosis in centre
  3. Inflamm response mediated by Type 4 Hypersensitivity reaction
65
Q

What is a Ghon complex?

A

Lung lesion + affected lymph nodes (by MAC migration in TB)

66
Q

How is TB similar to Nontuberculous mycobacterial infections? (3 things)

A
  1. Fatigue
  2. Dyspnoea
  3. Haemoptysis
67
Q

How can TB be differentiated from Nontuberculous mycobacterial infections? (2 things)

A
  1. TB has MORE fever + weight loss

2. Culture results

68
Q

How is TB similar to Pneumonia (4 things)

A
  1. Fever
  2. Dyspnoea
  3. Cough
  4. Chest pain
69
Q

How can TB be differentiated from Pneumonia? (2 things)

A
  1. Pneumonia has shorter duration of symptoms

2. Pneumonia responds to typical abx

70
Q

How is TB similar to Lung cancer (6 things)

A
  1. Fever
  2. Weight loss
  3. Cough
  4. Haemoptysis
  5. Chest pain
  6. Dyspnoea
71
Q

How can TB be differentiated from Lung cancer? (3 things)

A
  1. Sputum cytology
  2. CT of chest
  3. Tissue biopsy
72
Q

How is TB similar to Sarcoidosis cancer (2 things)

A
  1. Cough

2. Dyspnoea

73
Q

How can TB be differentiated from Sarcoidosis? (3 things)

A
  1. Sarcoidosis rarely forms cavities
  2. Sarcoidosis = negative sputum culture
  3. Sarcoidosis = non-caseating granulomas
74
Q

How is TB similar to Lymphoma? (3 things)

A
  1. Fever
  2. Night sweats
  3. Weight loss
75
Q

How can TB be differentiated from Lymphoma? (3 things)

A
  1. Lymphoma has RAPIDLY growing mass
  2. Lymphoma = absence of cough + dyspnoea
  3. Histopathology
76
Q

How is TB similar to a Lung abscess? (2 things)

A
  1. Cough with sputum production

2. Chest pain

77
Q

How can TB be differentiated from a Lung abscess? (3 things)

A
  1. Lung abscess = HIGH GRADE fever
  2. Lung abscess chest imaging shows infiltrates with cavity
  3. Culture results

#passmed 2022 (27 decks)

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