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103 Theme 4 - Lungs > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

TB is the commonest cause of infectious disease-related mortality worldwide?

True or false?

A

True

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2
Q

What fraction of global population have latent TB infection?

A

1/4

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3
Q

Is the global incidence of TB rising or falling?

A

Falling

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4
Q

Is the drug resistance prevelance rising or falling?

A

Rising

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5
Q

What % of TB patients are HIV infected?

A

8% HIV positive

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6
Q

The global prevelance of multi-drug resistant TB is lower in previously treated cases.

True or false?

A

False

Globally proportion of new cases with MDR TB is 3.4% new cases and 18.4% of previously treated cases

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7
Q

Is TB rising or falling in the UK?

A

Falling - less than 500 cases a year

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8
Q

People born outside of UK account for ____% of cases

A

72%

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9
Q

What is the pathophysiology of TB?

A
  • Airborne droplet spread
  • Inhaled – deposited in terminal airspaces
  • Macrophages ingest bacilli – replicate within endosomes
  • Transported to regional lymph node
  • Killed
  • Multiply → primary TB
  • Dormant → asymptomatic (LTBI if exposed to host immune system)
  • Proliferate after period of latency → reactivation disease
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10
Q

Complete the diagram

A

50%

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11
Q

What is the risk of developing active TB?

How is this risk different in HIV+ patients?

A

Risk of developing active TB 10-15% over lifetime in immunocompetent

HIV+: risk 10% per annum

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12
Q

What are the microscopic features of TB?

A
  • Aerobic bacillus
  • Divides every 16-20 hours (slow)
  • Cell wall, but lacks phospholipid outer membrane
  • Does not stain strongly with Gram stain (weakly positive)
  • Retains stains after treatment with acids

–Acid fast bacillus

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13
Q

What will you see in pathology in TB patients?

A

Granulomatous inflammation

  • Rim of lymphocytes
  • Fibroblasts
  • Central infected macrophages (giant cells)
  • Central necrosis – caseation
  • Secretion of cytokines (IFNγ) – activate macrophages to kill bacteria
  • AFBs (acid fast bacillus) in granulomas
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14
Q

What does this show?

A

Granulomatous inflammation

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15
Q

Who is at higher transmission risk?

A
  • Close contacts of infectious cases (smear +)
  • Contact with high risk groups:
  • High incidence country
  • Frequent travel to high incidence areas

•Immune deficiency:

  • HIV
  • Steroids
  • Chemotherapy and biologics
  • Nutritional deficiency (vit D),
  • Diabetes
  • End stage renal failure

•Lifestyle factors:

  • Drug/alcohol misuse
  • Homelessness/hostels/overcrowding
  • Prison inmates

Genetic susceptibility (twin studies of gene polymorphisms)

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16
Q

What is anti-TNF-alpha treatment?

A

Medication for TB causing immunosurpression

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17
Q

What happens during primary TB?

A

–Bacilli overcome immune system soon after initial infection

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18
Q

What risk factors increase reactivation?

A

–Risk of reactivation increases with immunosuppression

HIV + risk 10% per year

HIV – risk 1%

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19
Q

What point of disease progression are the majority of TB cases in?

A

Latent period

20
Q

What percentage of TB latent cases will reactivate?

A

2-23% cases – reactivation disease

21
Q

How is active TB diagnosed?

A
  • Identify the infected area
  • Isolate the organism
  • Obtain information regarding susceptibility to antibacterials
22
Q

How is latent TB diagnosed?

A

Identify immune response to TB proteins or TB-specific antigens

23
Q

What does the the tuberculin skin test (Mantoux) require?

A

–circulating memory T-lymphocytes

–ability to mount a delayed hypersensitivity reaction

24
Q

What are the negatives of the tuberculin skin test (Mantoux)?

A
  • Cross reactive with other Mycobacterial antigens so non-specific
  • Maybe be falsely negative in severely ill or immunosuppressed individuals
25
Q

What are Interferon Gamma Release Assays?

A

ELISPOT/ELISA: Enzyme linked immunological assay of release of interferon-gamma in whole blood following stimulation by specific tuberculosis antigen

26
Q

What are the pros and cons of using Interferon Gamma Release Assays to test for TB?

A
  • More specific than Mantoux
  • Correlates better with degree of exposure than Mantoux
  • Does not differentiate between latent infection and disease
27
Q

Name 2 Interferon Gamma Release Assays machines

A

T-Spot TB®

Quantiferon Gold®

28
Q

What type of TB makes up the majority of cases (55%)?

A

Pulmonary TB

29
Q

Which type of TB has infection risk and why?

A

Pulmonary TB

Cavitatory disease – more infectious

30
Q

What are the clinical features of pulmonary TB?

A

Cough

Weight loss

Haemoptysis

Fever

Chest pain

Night sweats

31
Q

How is pulmonary TB diagnosed?

A

–Chest imaging

–Sputum/BAL

32
Q

What does this chest x-ray show?

A

Upper zone consolidation - white upper zone air opacification

Prominent hilar lymph node

33
Q

Where is consolidation usually found on TB chest x-rays?

A

Upper zone

34
Q

What does this chest x-ray show?

A

Bilateral consolidation

35
Q

Where can extra-pulmonary disease from TB effect?

A

–Lymph nodes

–CNS

–Bone (Pott’s disease of the spine)

–Genitourinary system

–GI tract

–Disseminated/miliary

36
Q

What makes extrapulmonary disease more likely?

A
  • More common in non-UK born Asian origin
  • Reactivation
37
Q

What does this chest x-ray show?

A

Hilar Lymphadenopathy

38
Q

What is this?

A

TB Lymphadenitis

39
Q

What is TB Lymphadenitis?

A

•Often get worse on treatment

–Paradoxical reaction

  • Can form sinus tracts with chronic discharge
  • Cold abscess formation
40
Q

What does this show?

A

Tuberculous Pleural Effusion

41
Q

What are the clinical features of Disseminated/Miliary TB?

A
  • Fevers, sweats, weight loss and malaise very common
  • Respiratory symptoms in majority
  • GI or CNS symptoms in 20%

–Abdo pain, diarrhoea, abnormal LFTs

–Hepatomegaly in 50%

–Headache or confusion; altered mental state in 20%

42
Q

What does this chest x-ray show?

A

Miliary TB

43
Q

What other forms of TB are there?

A

•Skeletal TB

–Around 15-30% of all extrapulmonary cases

•Genitourinary TB

–Kidney/bladder/pelvic involvement

–Pus in urine but repeatedly negative standard cultures (sterile pyuria)

•TB enteritis

–Ileo-caecal commonest

–Weight loss, diarrhoea, blood in stools

•TB of the eye

–Any part of the eye

–Probably more common than we think

  • Pericardial TB
  • CNS TB

–TB meningitis

–TB arachnoiditis

–Tuberculoma

–(Spinal cord compression – extension of discitis)

–1% of all cases of TB

–6% of extrapulmonary TB in immunocompetent host

–More common in HIV coinfected patients

–Mortality 15-40% despite effective Rx (CDC)

44
Q

How is TB controlled in the UK?

A
  • Government global policy
  • Early diagnosis AND treatment (even if negative cultures/smear)
  • Optimal treatment and adherence (DOT/VOT/Section)
  • Contact tracing
  • PreventioN - BCG (Vaccination)
  • Latent treatment programs. Prevent TB becoming active
45
Q

What are the first line drugs for TB?

A

Standard treatment for TB is a minimum of 6 months:

2 months (initial phase) of Isoniazid, Rifampicin, Pyrazinamide and Ethambutol. Known as standard quadruple therapy.

Followed by:

4 months (continuation phase) of Isoniazid and Rifampicin Known as standard dual therapy

TB treatment is taken all together on an empty stomach 1 hour before breakfast; compliance is essential for cure.

N.B. If there is central nervous system involvement the continuation phase of treatment is extended to 10 months making a 12 month full treatment plan.

46
Q

What is first line treatment for latent TB?

A

Latent treatment : 3 months Rifampicin/Isoniazid 6 M isoniazid

47
Q

What are the side effects caused by the TB drugs?

A
  • Pyrazinamide: Hepatoxicity, joint pain, N&V
  • Rifampicin: Hepatoxicity, reddish colour to the urine
  • Isoniazid: Hepatoxicity ,fever, peripheral neuropathy and optic neuritis
  • Ethambutol: peripheral neuropathy, optic neuropathy and gout

All: nausea and skin rashes

103 Theme 4 - Lungs (21 decks)

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