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Tutorials > TB MDT 2018 > Flashcards

TB MDT 2018 Flashcards

1
Q

Fever, cough, weight loss and night sweats for 6 weeks

  • -Productive of white sputum
  • -Has noticed some streaks of blood over the last few days
  • -whatis the most probablediagnosis?
A

TB

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2
Q

what is the reactivation of Tb?

A

A condition in which a latent infection with MTB becomes symptomatic, often due to the patient being immunocompromised, typically many months or years after primary infection. Symptoms may include fever, night sweats, weight loss, and/or a productive cough (80% of secondary infections begin in the lungs). The patient is contagious. The treatment of choice is isoniazid, rifampin, pyrazinamide, and ethambutol for the first 2 months. Treatment is then continued with isoniazid and rifampin alone for 4 months.

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3
Q

what is the primary TB?

A

–Bacilli inhaled & implant in lung
–Tissue destruction due to the intense host immune response
2 possible outcomes (infectious dose / host immune system)
1)Latent tuberculosis infection (LTBI)
–Definition: primary infection without any pathological findings on radiological imaging; however, screening tests indicating previous infection with M. tuberculosis are positive.
–The lifetime risk of reactivation TB for a person with LTBI is about 5–10%.
2)Active primary tuberculosis (only 1–5% of cases): primary infection with radiological-pathological findings of tuberculosis (see “Diagnostics” below)

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4
Q

What’s the difference between TB disease and latent TB?

A

1)Infection with M. tuberculosis
–Primary infection
–Reactivation of latent infection
–Mycobacteria are growing & causing symptoms/signs of disease. Usually diagnosed in the microbiology laboratory
2)A person with LTBI usually has a positive TST or IGRA test but has no physical findings of TB disease and
the chest X-ray is normal or only reveals evidence of healed infection i.e. granulomas or calcification in the
lung, hilar lymph nodes or both. Persons with LTBI are asymptomatic and are not infectious.
–Antibiotics will be used at this stage to
keep the TB infection from becoming a disease.

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5
Q

Which one of the following is the typical appearance of TB disease on x-ray?

  • -Usually has extrapulmonary nodules
  • -Presents with a cavitating lesion(s)
  • -Typically affects the lung bases
  • -Commonly presents with a pleural effusion
  • -Typically presents with a normal x-ray
A

Presents with a cavitating lesion(s)

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6
Q

what else can present with cavitating lesions on CXR?

  • -Necrotising pneumonia
  • -abscess
  • -Malignancy
  • -Wegener’s granulomatosis
  • -All of the above
A

All of the above

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7
Q

what happens to cavitary lesions of TB?

A

These cavities may heal completely but more commonly with a region of fibrotic scarring

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8
Q

what is the tuberculoma?

A

A tuberculoma is a clinical manifestation of tuberculosis which conglomerates tubercles into a firm lump, and so can mimic cancer tumors of many types in medical imaging studies. Since these are evolutions of primary complex, the tuberculomas may contain within caseum or calcifications.

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9
Q

what is miliary tuberculosis?

A

Massive hematogenous dissemination of Mycobacterium tuberculosis bacilli from a pulmonary or extrapulmonary focus with multiple organ involvement. It commonly manifests with fevers and night sweats, weight loss, cough, and dyspnea. The term “miliary” refers to the characteristic chest x-ray findings of small, nodular densities of equal size that are scattered throughout the lungs (“millet seed” appearance) because the immune system has failed to properly isolate the pathogen.

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10
Q

You suspect active TB - Which one of the following microbiology tests will you send?

  • -Blood cultures
  • -Sputum for auramine stain
  • -Sputum for Gram stain
  • -Interferon gamma release assay
  • -Mantoux test
A

Sputum for auramine stain

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11
Q

what is the Auramine-rhodamine stain?

A

A method of bacterial staining used to visualize acid-fast bacilli (e.g., Mycobacteria). Binds to mycolic acid present in the cell wall, which results in reddish-yellow fluorescence.

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12
Q

Which one of the following is the most appropriate for patient with TB?

  • -Airborne precautions in a negative pressure room
  • -Airborne precautions in a neutral pressure room
  • -Contact precautions in a neutral pressure room
  • -Droplet precautions in a positive pressure room
  • -Standard precautions in the ED waiting room pending test results
A

Airborne precautions in a negative pressure room to prevent further spreading of the disease. Positive pressure is to prevent the patient from acquiring any disease

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13
Q

how TB is spread?

A
  • -airborne particles
  • -Acquired through inhalation which travel to terminal airways
  • -Others: chickenpox, measles
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14
Q

what are the airborne precautions?

A

Prevents transmission of organisms which remain infectious over long distances when suspended in the air

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15
Q

droplet vs airborne protection masks?

A

1) Surgical mask. Barrier to protect from large droplets
- -Used for flu etc.
2) N95 masks. Come in different sizes. Fit testing needed
- -Used for TB

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16
Q

do surgical masks effectively protect from airborne particles?

A

no, they do NOT

  • -effectively filter small particles from the air
  • -prevent leakage around the edge of the mask when the user inhales
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17
Q

does the N95 mask protect from airborne particles?

A
  • -Yes
  • -Tight fitting
  • -Covers the nose and the mouth
  • -Protects the wearer from inhaling airborne particles by filtering the air before it reaches the wearer.
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18
Q

what is the acid-fast stain?

A
  • -A staining technique that identifies organisms with high mycolic acid content (e.g., Mycobacterium, Nocardia). Stained organisms are considered acid-fast.
  • -Remember AFB not always MTB
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19
Q

what are the risk factors for MDR TB?

A
  • -Previous TB
  • -Contact with persons with TB
  • -Health care workers
  • -HIV co-infection
  • -Travel to an area with increased incidence of drug resistant TB
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20
Q

what is the extensively drug-resistant TB (XDR-TB)?

A

–resistance to at least isoniazid and rifampicin (i.e. MDR-TB),
plus
–resistance to any fluoroquinolone,
plus
–any one of the following second-line anti-TB injectable drugs (capreomycin, amikacin or kanamycin)

21
Q

Why do MDR and XDR matter?

A
  • -MDR and XDR TB = increased mortality
  • -Second line antibiotics are more toxic for patients
  • -Second line antibiotics cost more
  • -Second line antibiotics need to be taken for longer
    1) 20 months versus 6-9 months
    2) May be issues with compliance and side effects
22
Q

But what if there were no acid-fast bacilli seen on auramine stain? What would you do then?

A
  • -about need for 3 sputum specimens (ideally mornings on different days) to increase sensitivity.
  • -If they were all negative, proceed to bronchoscopy for definitive diagnosis.
23
Q

what are the options at bronchoscopy?

A

1) If parenchymal infiltrates
- -Broncho-alveolar lavage (BAL) for microbiology
2) If no parenchymal infiltrates but lymphadenopathy
- -Endobronchial ultrasound (EBUS) & biopsy

24
Q

pathology of TB?

A
  • -Initial TB (primary) infection:

- -Lung parenchymal lesion + enlarged hilar lymph nodes = Ghon complex

25
Q

Which of the following is the correct Anti-TB therapy?

  • -Rifampicin, Isoniazid, Penicillin, Ethambutol
  • -Rifampicin, Isoniazid, Pyrazinamide, Ethambutol
  • -Rifampicin, Isoniazid, Pyrazinamide, Ertapenem
  • -Rifampicin, Itraconazole, Pyrazinamide, Ertapenem
  • -Await susceptibility testing results
A

Rifampicin, Isoniazid, Pyrazinamide, Ethambutol

26
Q

first-line antibiotics for TB?

A

–2 months of Rifampicin, Isoniazid, Pyrazinamide, Ethambutol
–Intensive phase – rapidly  mycobacterial burden:
2 months – RIPE
–Then 4 months of Rifampicin and Isoniazid
–Consolidation phase – eradicate all bacteria
4 months - RI

27
Q

what is directly observed therapy (DOT)?

A
  • -Health care worker watches patient swallow each dose of medication
  • -DOT is the best way to ensure adherence
  • -Should be used with all intermittent regimens
  • -Reduces relapse of TB disease and acquired drug resistance
28
Q

Which one of the following is a recognized side effect of isoniazid?

  • -Discoloration of bodily secretions
  • -Erythema nodosum
  • -Hair loss
  • -Peripheral neuropathy
  • -Retrobulbar neuritis
A

Peripheral neuropathy

29
Q

principles of TB Drug monitoring??

A
  • -Hepatotoxicity:
  • -Pretreatment LFTs and 2 weeks after starting RIPE
  • -Stop all drugs if transaminases >5 times normal
  • -Give vitamin B6 (pyridoxine) with isoniazid – prevents peripheral neuropathy
  • -Prior to commencing ethambutol – ophthalmology review for visual acuity and colour discrimination
  • -Rash – caused by all RIPE drugs
  • -Drug fever
30
Q

Who else do you need to tell your patient has tb?

  • -Your local public health department
  • -The national disease surveillance center
  • -No need to notify– the results are available on the hospital IT system
  • -No need to notify – somebody else will do it
  • -No need to notify – I need to respect the patient’s confidentiality
A
  • -Your local public health department
  • -TB is a notifiable disease which means that clinicians and laboratories have a statutory (legal) obligation to notify all cases to the Director of Public Health
31
Q

Your patient lives at home with his wife and 2 children – what should happen next?

  • -The public health department should assess them
  • -I will ask them to attend the respiratory clinic for assessment
  • -If they are asymptomatic, nothing needs to happen
  • -If they are asymptomatic, I will give them an information leaflet on TB and ask them to visit their GP if they develop symptoms
A

The public health department should assess them

32
Q

Aims of contact tracing?

A
  • To identify and initiate treatment of secondary cases
  • To identify TB infected contacts in order to offer treatment for LTBI
  • To identify those not infected for whom BCG vaccination may be appropriate
33
Q

Role of the public health doctor in TB?

A
  • -Identification and management of contacts of TB cases following notification to Public Health by the clinician or laboratory
  • -Involvement in the co-ordination of DOT following discussion with the treating physician ±case conference
  • -Investigation and management of TB outbreaks in the community
34
Q

What is considered an infectious case?

A

1) Sputum smear positive for acid-fast bacilli (AFB)
2) BAL smear positive (but sputum negative) presumed infectious if:
- -There are cavities on CXR
- -MDR or XDR-TB suspected
- -Contacts are immunosuppressed or children <5yrs

35
Q

Who is at risk of acquisition of pulmonary TB from an infectious case?

A

1) Depends on the duration of exposure, the infectiousness of case and vulnerability of contact
2) A person has deemed an at-risk “contact” if
- -Exposure to an infectious case equivalent to 8 hours conversation time
- -Or 4 hours if patient <5yrs old/ HIV positive/ immunocompromised
3) 10% of those who get infected will develop TB disease at some point in their lives
4) Household, work, social contacts may be at risk.

36
Q

does everyone exposed become infected?

A

Not everyone exposed becomes infected! Probability of transmission depends on:
Infectiousness, type of environment, Length of exposure

37
Q

Which of the following will public health use for the initial screening of contacts?

  • -CT thorax
  • -Interferon beta release assay
  • -Mantoux test
  • -TB PCR
A

Mantoux test

38
Q

what is the Mantoux test?

A
  • -Intradermal injection of protein derived from M. tuberculosis bacteria
  • -Local skin reaction used to assess a person sensitivity to the tuberculin protein
  • -Person with cell-mediated immunity to M. tuberculosis have:
    1) Cell-mediated delayed hypersensitivity reaction within 48 to 72 hours
    2) Localized swelling/ induration of the skin at the injection site
    3) The greater the reaction, the more likely it is that an individual has TB (LTBI or TB disease)
    4) A positive test generally means that a person is infected with TB
39
Q

after a positive Mantoux test, what should be done to confirm the active disease?

A

After a positive test, an X-ray or sputum (coughed up phlegm) sample is
needed to confirm the active disease.

40
Q

what are the causes of false-negative Mantoux test?

A

–ten percent of persons with active disease may be non-reactors due to other underlying conditions such as malnutrition, malignancy and alcohol use. HIV infected persons lose tuberculin reactivity as their immune suppression progresses.

41
Q

what are the causes of the false-positive Mantoux test?

A
  • -Nontuberculous mycobacterial infection (Reactions usually ≤10mm induration)
  • -BCG vaccination in past (Reactivity generally wanes over time)
  • -Known BCG-vaccinated persons with positive Mantoux still need to be evaluated for presence of TB infection
42
Q

what is the IGRA?

A
  • -T-cells which have been in the previous contact with TB antigens release high levels of gamma interferon when they are re-exposed to the same TB antigens
  • -Blood test is taken from the patient
  • -2 types of essays are available
    1) One measures the amount of gamma interferon
    2) The other measures the number of M. tuberculosis sensitive T-cells in the blood
  • -T-cells which have not been in contact with the bacterium will not release gamma interferon
43
Q

Can IGRA distinguish between active TB and LTBI?

A

no

44
Q

does IGRA is more specific for TB infection than Mantoux?

A

yes

45
Q

what is the interpretation of the Mantoux test?

A

1) ≥ 5 mm, positive
-HIV-positive patients
–Recent contact with a TB-infected person
–Signs of TB on chest x-ray
2)≥ 10 mm
–Patients with a high risk of reactivation
–IV drug use
–Homelessness
–Immigration from an endemic country
–Chronic illness (e.g., diabetes, kidney or lung disease, malignancy)
–Occupation (health care or prison workers)
3)≥ 15 mm, highly positive, may have partial blistering
Always considered positive, even without risk factors

46
Q

what is the treatment of latent TB?

A

Isoniazid x 6 months
OR
Isoniazid + rifampicin x 3 months

47
Q

what is the follow up of TB?

A

1) Repeat chest x-ray at
- -2 months
- -End of treatment
2) Repeat sputum microscopy at
- -2 months: If sputum smear positive for AFB at 2 months, intensive phase should be prolonged by 1 month
- -5 months
- -End of treatment

48
Q

What if the patient had Multi-drug resistant TB (MDR-TB)?

A

1)Initial intensive phase:
–Prolonged for more than 2 months
–Additional anti-TB medications (e.g five or more agents)
Consolidation phase:
2)Prolonged beyond 4 months
–Additional anti-TB medications
–In general MDR-TB should be treated by a specialist
–Extrapulmonary TB also requires longer intensive and consolidation phases with drugs selected based on their penetrance into affected tissues

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