TB Flashcards
1
Q
What factors increase the likelihood of someone having TB? (6 things)
A
- Hx prior TB exposure / treatment
- Low immunity (HIV)
- Travel to area where TB is endemic
- Homelessness
- Jail / IV drug use
- Gastrectomy
2
Q
What are the classical features of pulmonary TB? (7 things)
A
- Fever
- Night sweats
- Fatigue
- Cough
- Haemoptysis
- Chest pain
- Weight loss / anorexia
3
Q
What is the bacteria that causes TB?
A
Myobacterium tuberculosis
4
Q
When does active infection of TB occur?
A
Inadequate containment by immune system (T cells / macrophages)
5
Q
What 2 things can active infection of TB arise from?
A
- Primary infection
2. Reactivation of latent disease
6
Q
What is latent TB?
A
Infection without disease
Because contained by immune system (e.g granuloma formation prevents bacteria growth + spread)
7
Q
What tests will show up positive / negative in latent TB?
A
Positive: skin / blood tests
Negative: Sputum / CXR
8
Q
What are the risk factors for reactivating latent TB?
A
- New infection
- HIV
- Organ transplant
- Immunosuppression
- Homeless / jail
9
Q
What are the systemic clinical features of TB? (7 things)
A
- Fever (low grade)
- Anorexia
- Malaise
- Weight loss
- Night sweats
- Erythema nodosum (red + swollen fat under skin)
- Clubbing (bronchiectasis)
FAM W NEC
10
Q
What are the clinical features of PULMONARY TB? (4 things)
A
- Cough (dry then productive)
- Haemoptysis
- Pleurisy (inflamm pleura)
- Pleural Effusion
11
Q
What are the clinical features of Tuberculus Lymphadenitis? (2 things)
A
- Painless enlargement of cervical / supraclavicular lymph nodes
- Systemic symptoms (FAM W NEC)
12
Q
What are the nodes like in Tuberculus Lymphadenitis?
A
Firm to touch and NOT acutely inflamed
13
Q
Does Tuberculus Lymphadenitis occur with PULMONARY TB?
A
Yes and can also occur without
14
Q
How is Tuberculus Lymphadenitis investigated? (3 things)
A
- Fine needle aspiration
- AFB staining (sputum stain for Mycobacteria)
- Culture
FAC
15
Q
What are the clinical features of GASTROINTESTINAL TB? (3 things)
A
- Vomiting
- Colicky abdominal pain
- Bowel obstruction (bc bowel wall thickening / stricture)
16
Q
What is required for the diagnosis of GASTROINTESTINAL TB?
A
Biopsy
17
Q
What distinguish GASTROINTESTINAL TB from Crohn’s disease? (2 things)
A
Caseation necrosis
Absence of transmural cracks
18
Q
What are the clinical features of SPINAL TB? (4 things)
A
- Pain + bony tenderness for weeks / months
- Bony destruction / vertebral collapse
- Soft tissue abscess
- Slow progression
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
20
Q
What is CNS TB?
A
Haematogenous spread leading to foci of infection in brain + spinal cord
21
Q
What do foci of CNS TB enlarge to form?
A
Tuberculomas
22
Q
What does foci of CNS TB rupture lead to?
A
Meningitis
23
Q
What should you check the CSF for in CNS TB? (4 things)
A
- Leucocytosis
- Raised protein
- Plasma glucose <50%
- AFB stain, PCR & culture
24
Q
What are the clinical features of GENITOURINARY TB? (5 things)
A
- Dysuria
- Frequency
- Loin pain
- Haematuria
- Sterile pyuria (WBC in urine)
25
What can granulomas in GENITOURINARY TB cause?
1. Fibrosis
2. Strictures
3. Infertility
4. Genital ulceration
26
What does CARDIAC TB involve?
Pericardium (pericarditis, pericardial effusion, constrictive pericarditis)
27
What are the diagnostic tests for latent TB? (2 things)
1. Tuberculin skin testing (TST) (aka Mantoux test)
| 2. Interferon-gamma release assays (IGRAS)
28
What reduces sensitivity of both latent TB tests?
Immune suppressed states
29
What are the diagnostic tests for active TB? (4 things)
1. CXR
2. Sputum smear
3. Sputum culture
4. Nucleic acid amplification test (NAAT)
30
What is seen in a CXR in active TB? (4 things)
1. Cavitation (mainly upper lobe if reactivated TB)
2. Calcification
3. Effusion (yh)
4. Lymphadenopathy
(Caseating necrosis seen in histology)
31
How many specimens of sputum smear are needed for TB diagnosis?
3 specimens
| Including an early morning sample
32
What is the sputum smear stained for in TB diagnosis?
For presence of acid-fast bacteria (AFB)
33
If AFB is seen on the sputum smear (in TB diagnosis), what are your next steps? (2 things)
1. Start treatment
| 2. Isolate patient
34
Why is sputum culture better than sputum smear?
More sensitive
35
How long does sputum culture take?
1-3 weeks (liquid)
| 4-8 weeks (solid)
36
What does Nucleic acid amplification test (NAAT) do in diagnosing TB?
Directly detects M. tuberculosis in sputum by DNA / RNA amplification
Rapid diagnosis (under 24 - 48 hours)
37
How is EXTRAPULMONARY TB diagnosed?
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
What are the first line abx for TB treatment?
Rifampicin
Isoniazid
Pyrazinamide
Ethambutol
RIPE
39
How does Rifampicin affect enzymes?
It is an Enzyme Inducer
So take care with:
1. Warfarin
2. Calcineurin inhibitors (immunosuppressive drugs)
3. Oestrogens
4. Phenytoin (seizure drug)
40
What are some irrelevant side fx of Rifampicin? (2 things)
1. Turns body secretions orange
(urine / tears)
2. Flu like symptoms
41
What is an important side fx of Rifampicin?
Altered liver function (Hepatotoxicity)
42
What are the side fx of Isoniazid? (3 things)
1. Peripheral neuropathy (bc X form pyridoxine aka vit B6)
2. Hepatoxicity - Enzyme Inhibitor / Hepatitis
3. Agranulocytosis (low WBC)
43
How is the side fx of Isoniazid overcome?
Give with prophylactic pyridoxine (Vit B6)
44
What are the side fx of Isoniazid? (3 things)
1. Peripheral neuropathy (bc X form pyridoxine aka vit B6)
2. Hepatoxicity - Enzyme Inhibitor / Hepatitis
3. Agranulocytosis (low WBC)
45
What are the side fx of Pyrazinamide? (4 things)
1. Hyperuricaemia causing gout
2. Arthralgia (joint pain) / Myalgia (muscle pain)
3. Hepatotoxicity
4. Kidney problems
46
When should the dose of Pyrazinamide be reduced?
If the eGFR is below 30
47
What is the side fx of Ethambutol?
1. Colour blindness
2. Reduced visual acuity
3. Optic neuritis
48
What should be checked before and monitored during when Ethambutol is diagnosed?
Visual acuity
49
What is the recommended dose of Rifampicin for the average adult (over 50kg)?
600 mg once daily for 6 months
50
What is the recommended dose of Isoniazid for the average adult (over 50kg)?
300 mg daily for 6 months
51
What is the recommended dose of Pyrazinamide for the average adult (over 50kg)?
2 g once daily for 2 months (initial phase).
52
What is the recommended dose of Ethambutol for the average adult (over 50kg)?
15 mg/kg once daily for 2 months
53
What is the mechanism of action of Rifampicin?
Inhibits bacterial DNA-dependent RNA polymerase --> prevents transcription of DNA into mRNA
54
What is the mechanism of action of Isoniazid?
Inhibits mycolic acid synthesis
55
What is the mechanism of action of Pyrazinamide?
It is converted by pyrazinamidase --> pyrazinoic acid which inhibits fatty acid synthase (FAS)
56
What is the mechanism of action of Ethambutol?
Inhibits arabinosyl transferase (enzyme) which polymerizes arabinose --> arabinan
57
Which patients need their Ethambutol dose adjusted?
Patients with renal impairment
58
Where does dormant tuberculosis most frequently reactivate?
And why?
Lung APEX
Because most oxygenated area --> allows faster myobacteria multiplication + spreading
59
What is the general pathophysiology of TB? (6 steps)
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
What (AFB) stain is used to identify myobacteria in TB diagnosis?
Ziehl-Neelsen stain
61
What is the histological finding in patients with granulomas resulting from a TB infection?
Epithelioid histiocytes
62
Why is an AFB smear alone insufficient in achieving a definitive diagnosis for TB?
AFB smear is not specific for TB - all mycobacteria will stain positive
63
What is the order of sensitivity of active TB diagnostic methods?
Culture (most sensitive)
NAAT
Smear
64
What is the histological pathophysiology of TB? (3 steps)
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
What is a Ghon complex?
Lung lesion + affected lymph nodes (by MAC migration in TB)
66
How is TB similar to Nontuberculous mycobacterial infections? (3 things)
1. Fatigue
2. Dyspnoea
3. Haemoptysis
67
How can TB be differentiated from Nontuberculous mycobacterial infections? (2 things)
1. TB has MORE fever + weight loss
| 2. Culture results
68
How is TB similar to Pneumonia (4 things)
1. Fever
2. Dyspnoea
3. Cough
4. Chest pain
69
How can TB be differentiated from Pneumonia? (2 things)
1. Pneumonia has shorter duration of symptoms
| 2. Pneumonia responds to typical abx
70
How is TB similar to Lung cancer (6 things)
1. Fever
2. Weight loss
3. Cough
4. Haemoptysis
5. Chest pain
6. Dyspnoea
71
How can TB be differentiated from Lung cancer? (3 things)
1. Sputum cytology
2. CT of chest
3. Tissue biopsy
72
How is TB similar to Sarcoidosis cancer (2 things)
1. Cough
| 2. Dyspnoea
73
How can TB be differentiated from Sarcoidosis? (3 things)
1. Sarcoidosis rarely forms cavities
2. Sarcoidosis = negative sputum culture
3. Sarcoidosis = non-caseating granulomas
74
How is TB similar to Lymphoma? (3 things)
1. Fever
2. Night sweats
3. Weight loss
75
How can TB be differentiated from Lymphoma? (3 things)
1. Lymphoma has RAPIDLY growing mass
2. Lymphoma = absence of cough + dyspnoea
3. Histopathology
76
How is TB similar to a Lung abscess? (2 things)
1. Cough with sputum production
| 2. Chest pain
77
How can TB be differentiated from a Lung abscess? (3 things)
1. Lung abscess = HIGH GRADE fever
2. Lung abscess chest imaging shows infiltrates with cavity
3. Culture results
