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Leicester Year 3 GP > GP/ medicine - Tuberculosis > Flashcards

GP/ medicine - Tuberculosis Flashcards

1
Q

What microorganism causes TB?

A

Mycobacteria tuberculosis

But can also be caused by Mycobacteria bovis and Mycobacteria africanum

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2
Q

Is Mycobacteria tuberculosis a bacillus or a coccus?

A

A bacillus (rod)

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3
Q

Can normal gram stain differentiate M.tuberculosis from other bacteria?

A

NO!

M.tuberculosis is special in the sense that it cannot be stained by normal gram stain i.e. neither gram + nor gram.

It’s an acid-fast bacilli, which means it can only be stained with acid-fast stain

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4
Q

What acid-fast stain do we normally use to identify mycobacteria? what color does that stain have?

A

Ziehl-Neelsen stain

It’s a light-blue stain

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5
Q

On a CXR, where would you usually see the consolidation in a patient with TB?and why?

A
  • Upper lung lobes (usually at the apex) because it’s where most oxygen is present and TB is an aerobe!
  • Cavitation, pleural effusion, mediastinal or hilar lymphadenopathy

Oxygen makes TB have orgasm!!!!

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6
Q

Compare and contrast TB and pneumonia

A
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7
Q

Where in the world TB is usually found?

A

Asia, Africa, South America, Eastern Europe

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8
Q

How is TB transmitted?

A

Aerosol inhalation causes pulmonary infection

Then from the lungs, it can spread all over the body through blood (haematogenous spread), causing extrapulmonary TB

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9
Q

What is the pathology/ pathogenesis of TB?

A
  • Infected aerosols inhaled into the lungs
  • Alveolar macrophages engulf the bacteria and carry them to hilar lymph nodes in attempt to control infection
    • The lung lesion (Ghon focus) + hilar lymph nodes = Ghon complex
  • Small granulomas (tubercles) are formed by macrophages to wall off and contain TB, preventing it from spreading.
    • Granulomas are basically a collection of epitheliod histiocytes, lymphocytes and Langerhans giant cells surrounding a cheese-like core, which indicates caseous necrosis in the centre
    • If infection is not adequately contained by granulomas, it can invade the bloodstream and cause Extrapulmonary TB and Miliary TB
  • The inflammatory response is mediated by a type 4 hypersensitivity reaction
  • Progression of TB then follows one of two paths:
    • Active disease (primary TB) - symptomatic and infectious - the most common presentation (> 50%), OR
    • Latent disease - asymptomatic and NOT infectious - of which there are 2 outcomes:
      • Heals spontaneously and no disease develops - common in healthy individuals
      • Reactivation –> secondary TB (or post-primary TB) which is an active disease - patient is symptomatic and infectious
        • Usually occurs if a patient becomes immunocompromised e.g. old age, HIV, malignancy, steroids, malnutrition
        • The lungs remain the most common site for secondary TB, however, extrapulmonary TB and miliary TB may occur in immunocompromised patients, esp in the following areas:
          • CNS –> TB meningitis (most serious complication)
          • Vertebral bodies –> Pott’s disease
          • Cervical lymph nodes –> Scrofuloderma
          • Renal
          • GI tract
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10
Q

What are the risk factors for TB?

A

PMHx of TB

Close contact with someone with TB

Born in a country with high TB incidence e.g. India, Pakistan, Bangladesh

Foreign travel to country with high TB incidence

Immunosuppression e.g. HIV, organs transplant recipients, renal failure/ dialysis, malnutrition, diabetes, steroids, chemotherapy

Hx of alcohol excess, smoking, and IVDU

Children < 5 yrs old (higher risk of developing extrapulmonary TB)

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11
Q

Give 3 complications of TB

A

Bronchiectasis

Multi-drug resistance (MDR) TB

COPD

Cor pulmonale

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12
Q

What are the symptoms and signs of pulmonary TB?

A

Symptoms of pulmonary TB:

  • Persistent productive cough with purulent sputum
  • Fever
  • Weight loss
  • Drenching night sweats
  • Haemoptysis (late)
  • Dyspnoea

Signs:

  • Crackles and bronchial breathing
  • Pleural effusion
  • If severe –> atelectasis, pneumonia, bronchiectasis
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13
Q

What are the clinical features of extrapulmonary TB?

A
  • Genitourinary - sterile pyuria, salpingitis, abscess, epididymitis in males, haematuria
  • MSK - arthritis, pott’s disease (back pain), osteomyelitis
  • CNS - TB meningitis (headache, photophobia, neck stiffness, confusion, cranial nerve abnormalities, vomiting)
  • GI - Ileocaecal lesions - abdominal/ pelvic pain, constipation, bowel obstruction, hepatosplenomegaly
  • Skin - erythema nodosum, scrofuloderma
  • Lymph nodes - lymphadenopathy often affecting cervical or supraclavicular lymph nodes
  • Cardiac - TB pericarditis (pericardial rub, Kussmaul’s sign, fever, cardiomegaly, cough, SOB, chest pain, ankle swelling) –> pericardial effusion and tamponande
    • Kussmaul’s sign = a paradoxical rise in jugular venous pressure (JVP) on inspiration, or a failure in the appropriate fall of the JVP with inspiration.

Miliary (disseminated)

. .

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14
Q

What are the differentials for haemoptysis?

A

PE

Bronchiectasis

TB

Pneumonia

Lung cancer

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15
Q

What investigations would you carry out to screen for latent TB?

A

CXR

quantiFERON (IGRA) or T-spot test

Mantoux test (tuberculin sensitivity test)

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16
Q

What are the limitations of quantiFERON?

A
  1. It only tells you whether you have previously been infected with TB i.e. latent TB infection. It doesn’t differentiate between active and latent TB
    * A + quantiFERON test does not mean that the patient has active TB and a - quantiFERON test does not mean that the patient doesn’t have active TB
  2. Patients with immunosuppression may not release IFN-y, causing false negatives
  3. It can’t pick up non-TB mycobacteria
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17
Q

How does quantiFERON work?

A

It detects the amount of IFN-y released by T cells when they are exposed to proteins found on mycobacteria. Pre-exposed cells release more IFN-y

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18
Q

Why is IGRA a better test over the Mantoux test?

A
  • It can distinguish latent TB from previous BCG vaccine
  • It can distinguish TB mycobacteria from non-TB mycobacteria, so it won’t give any false positives if the patient is infected by non-TB mycobacteria. It only gives a positive result if it’s caused by TB-mycobacteria
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19
Q

What is Mantoux? How is it being carried out?

A

0.1 mL of purified protein derivative (PPD) injected intradermally

Result read 2-3 days

Erythema and induration > 10 mm = positive result - this implies previous exposure to TB including BCG vaccine

If strongly positive (> 15 mm), TB is likely (as response to previous BCG decreases with time), needs further investigation including e.g. CXR, sputum smear

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20
Q

Causes of false-positive Mantoux test

A

Previous BCG vaccination

Infection with non-TB mycobacteria

Incorrect method of TST administration

Incorrect interpretation of reaction

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21
Q

Causes of false-negative Mantoux test

A

Immunosuppression - miliary TB, AIDS, steroids

Sarcoidosis

Lymphoma

Extremes of age

Fever

Hypoalbuminaemia, anaemia

22
Q

How do you differentiate active TB from latent TB?

A

Usually based on symptoms and findings on CXR

But the following investigations can help too:

  • Sputum smear microscopy (with Ziehl-Neelsen stain)
  • TB culture
  • NAAT
  • Histology - TB granuloma
23
Q

Which group(s) of people needs IGRA screening for latent TB ?

A

IGRA tests are used in asymptomatic patients who are at high risk of latent TB infection:

  • Immigrants from high TB prevalence countries
  • Healthcare workers
  • People who have been in contact with a person with active pulmonary or laryngeal TB
  • Patients who are immunocompromised e.g. HIV + patients, organ transplant recipients
  • For people who have evidence of TB scarring or untreated fibrotic changes on chest X-ray but have not completed treatment as planned
24
Q

What investigations would you carry out in someone with active TB?

A
  • CXR - cavitation/ pleural effusion/ mediastinal or hilar lympadenopathy
  • CT - lymphadenopathy/ nodes with central necrosis
  • MRI - leptomeningeal enhancement in TB meningitis
  • TB culture (gold standard) - however this can take 6 weeks:
    • Pulmonary TB - send 3 sputum samples for sputum smear microscopy and culture
    • Meningeal TB - lumbar puncture
    • Pericardial TB - pericardiocentesis
    • Gastrointestinal TB - colonoscopy + biopsy
    • Lymph node TB - biopsy of lymph node
  • Histology - shows caseating granulomas
  • Blood tests - FBC, U&Es, LFT
  • HIV test
  • Check vitamin D

In primary care:

  • CXR + 3 sputum samples if active pulmonary TB
  • Be aware that false negative results are more common in children and the immunocompromised, such as people with HIV.
25
Q

What investigations would you carry out in pulmonary TB?

A

Pulmonary TB - x3 sputum samples​ for sputum smear microscopy with Ziehl-Neelsen stain

  • If ‘smear +’ = high bacterial load and high infectivity –> start anti-TB treatment right away as there is a high chance it will culture
  • If ‘smear -‘ –> bronchoscopy +/- EBUS (endobronchial ultrasound guided biopsy) of pulmonary lymp nodes –> start anti-TB treatment

CXR

CT chest if clinical features/ CXR atypical

26
Q

What investigations would you carry out with meningeal TB?

A

MRI head followed by lumbar puncture

  • MRI head shows leptomeningeal enhancement
  • Lumbar puncture for TB culture and TB PCR - shows low glucose, high protein, lymphocytosis, fibrin web

(Note that ALL patients with miliary TB should have a lumbar puncture + CT/MRI head done to exclude TB meningitis as TB meningitis the most serious complication)

27
Q

What are the clinical features of TB meningitis?

A

Headaches, photophobia, neck stiffness, confusion, vomiting, personality change

More insidious onset compared to viral/bacterial meningitis

28
Q

What investigations would you do for pericardial TB?

A

Pericardiocentesis for TB culture

29
Q

What clinical features will you see in pericardial TB?

A

Pericardial rub, Kussmaul’s sign, fever, cardiomegaly, cough, SOB, chest pain, ankle swelling

It can cause pericardial effusion and cardiac tamponade

30
Q

What investigations would you carry out for disseminated/ miliary TB?

A
  • CXR/ CT - shows widespread consolidations
  • MRI head followed by lumbar puncture to exclude CNS involvement
31
Q

What is the initial management for TB?

A
  • ABCDE
  • Admit to side room + start infection control measures e.g. masks and negative pressure room
  • If productive cough: send 3 sputum samples for sputum smear microscopy and TB culture
    • If no productive cough but pulmonary TB suspected –> bronchoscopy
  • Routine bloods (FBC, U&Es, LFTs) + HIV test and check vitamin D levels
  • CT chest if pulmonary TB suspected but clinical features or CXR atypical
  • CT/ MRI head + lumbar puncture if miliary TB is suspected to exclude CNS involvement
  • If diagnosis between pneumonia and TB is unclear: always treat it initially as pneumonia, so start Abx for pneumonia according to CURB-65 score, while investigating for TB
  • If patient critically unwell and high likelihood of TB (no time to wait for sputum results) then start anti-TB therapy AFTER sputum samples sent
  • TB is a notifiable disease so inform case to TB nurse specialists and public health team + start contact tracing
32
Q

What is the pharmacological mangement of TB?

A

For latent TB:

  • Rifampicin + Isoniazid (+ pyridoxine) for 3 months
    • Assess risk of hepatotoxicity

For active TB:

  • Standard RHZE treatment for 6 months for all sites EXCEPT for CNS TB (which needs 12 months):
    • Rifampicin + Isoniazid (+ pyridoxine) + Pyrazinamide + Ethambutol for 2 months, then continue Rifampicin + Isoniazid (+ pyridoxine) only for 4 months
  • For meningeal/ pericardial/ spinal TB:
    • Give steroids at the start of treatment on top of the standard RHZE treatment to prevent paradoxical reaction
  • For meningeaI TB:
    • Standard RHZE treatment for 12 months + steroids at the start of treatment
      • Rifampicin + Isoniazid (+pyridoxine) + Pyrazinamide + Ethambutol for 2 months, then continue Rifampicin + Isoniazid (+ pyridoxine) only for 10 months + steroids at the start of treatment
  • For disseminated/ miliary TB:
    • Do CT/ MRI head + lumbar puncture to see if there is CNS involvement
      • If no CNS involvement –> standard RHZE treatment for 6 months (+ steroids if pericardial involvement)
      • If there is CNS involvement –> standard RHZE treatment for 12 months + steroids at the start of treatment)
  • For MDR and non-MDR resistant TB
    • Usually seen in patients from abroad, esp in those who have had incomplete treatment for TB previously
    • Treatment regimen is decided by the consultant
    • Infection control - manage patients in a negative pressure room + staffs wear PPE/ masks
33
Q

Does latent TB require notification to public health? does it need contact tracing?

A

NO and NO

34
Q

Before starting RHZE treatment, what must you monitor?

A

Baseline LFTs (as rifampicin, isoniazid, pyrazinamide are hepatotoxic)

Visual acuity (as ethambutol can cause reduced visual acuity)

35
Q

What should you do if LFTs become deranged during standard RHZE treatment?

A

Treatment can either be stopped and the drugs gradually reintroduced once LFTs have normalised, OR a “liver friendly” regimen can be given (e.g. amikacin, levofloxacin, and ethambutol) but the treatment duration is longer, up to 24 months

36
Q

How long should you give RHZE treatment for non-meningeal TB?

A

6 months

(4 drugs for 2 months, then 2 drugs for 4 months)

37
Q

How long should you give standard RHZE treatment for meningeal/ CNS TB?

A

12 months

(4 drugs for 2 months, then 2 drugs for 10 months)

38
Q

Which extrapulmonary TB needs steroids at the start of treatment to prevent paradoxical reaction?

A

Meningeal/ pericardial/ spinal TB

39
Q

What drug must you give alongside isoniazid to prevent peripheral neuropathy?

A

Pyridoxine (vitamine B6)

40
Q

What are the side effects of rifampicin?

A
  • Rifampicin
    • Orange tears and urine
    • Hepatitis
    • Rashes
    • Rifampicin is a CYP450 enzyme inducer, so it can increase the rate at which drugs like warfarin and COCP being metabolised in the liver
41
Q

What are the side effects of isoniazid?

A

Isoniazid:

  • Peripheral neuropathy (reduced by pyridoxine)
  • Hepatitis
  • Rashes
  • Psychosis
  • Colour blindness

• Pyrazinamide – Hepatitis, rashes, vomiting, arthralgia • Ethambutol – Retrobulbar neuritis Therefore, MUST do a baseline visual acuity test and LFT’s which must be monitored closely

42
Q

What are the side effects of pyrazinamide?

A

Pyrazinamide:

  • Hepatitis
  • Rashes
  • Vomiting
  • Arthralgia

Ethambutol – Retrobulbar neuritis Therefore, MUST do a baseline visual acuity test and LFT’s which must be monitored closely

43
Q

Which anti-TB drug causes arthralgia as a side effect?

A

Pyrazinamide

44
Q

What are the side effects of Ethambutol?

A

Ethambutol:

  • Retrobulbar neuritis –> reduced visual acuity
45
Q

How is contact tracing performed?

A

Test household contacts with either CXR or quantiFERON and treat any latent TB

46
Q

What vaccine do you give to babies to prevent TB infection? What type of vaccine is that?

A

BCG vaccine (live attenuated vaccine)

47
Q

What are the guidelines for infection control for TB?

A
  • Staffs do NOT need to wear masks/ aprons unless MDR TB is suspected or they are performing an aerosol generating procedure e.g. giving a nebuliser
  • Patients with smear + TB need to wear a mask when leaving their room until they have completed 2 weeks of treatment. After 2 weeks of treatment, patients are generally considered non-infectious to immunocompetent individuals
  • Patients with non-resistant pulmonary TB should be nursed in a side room
  • If the ward also manages immunocompromised patients, including HIV (i.e our ward!) then patients with pulmonary TB need to be nursed in a side room until discharge regardless of whether they are smear positive or negative
48
Q

Give 3 differential diagnoses for TB

A

Viral URTI

Asthma

COPD

49
Q

What advice can you give to the patient with TB?

A

Advice:

  • Encourage adherence to the treatment regimen
  • Lifestyle changes - stop smoking and drinking
  • Advise that pulmonary TB can be transmitted to close contacts, and screening via contact tracing will be arranged for high-risk contacts (usually household contacts)
  • Advise on symptoms suggesting relapse after treatment completion and the need to inform local TB team or primary care immediately
  • Safety netting: If symptomatic or if acutely deteriorating, call 999 and inform local TB team
50
Q

When should you refer TB patients?

A
  • Suspected active TB
  • If the person has known active or latent TB but has not completed treatment as planned
51
Q

What investigation is best used for assessing drug sensitivities in TB?

A

Sputum culture

Leicester Year 3 GP (36 decks)

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