Asthma & Respiratory Immunology Flashcards
Outline the epidemiology of asthma.
- 5.4 million people in the UK currently receiving treatment for asthma
- 1.1 million children affected (approx. 3 in every class)
- On average, 3 people die of an asthma attack every day in the UK
- NHS spends approx. £1billion annually treating asthma
What are the risk factors of asthmas (3)?
- Genetic susceptibility
- Allergies / Allergic diseases
- Environmental exposures
Outline the aetiology of asthma.
How would a patient with suspected asthma present (5)?
- Wheeze +/- Dry cough +/- Dyspnoea
- Persistent symptoms + episodes (attacks) – precipitated by exertion, colds, allergen exposure
- Atopy / allergen sensitisation
Outline the pathophysiology of asthma.
- Airway eosinophilia
- Airway inflammation / narrowing on baseline
- Reversible airway obstruction
How would one diagnose suspected asthma (6)?
-
Clinical assessment:
- History & examination
- Assess / confirm wheeze when acutely unwell (doctor diagnosed wheeze)
-
Objective tests:
- FBC
- Airway obstruction on spirometry - FEV1/FVC ratio < 0.7 (adults), < 0.8 (children)
- Reversible airway obstruction - Bronchodilator reversibility > 12%
- Exhaled nitric oxide (FeNO) >35ppb (children), > 40ppb (adults) – in a treatment naïve patient
What airway obstruction on spirometry would confirm asthma on an adult?
FEV1/FVC ratio < 0.7
What airway obstruction on spirometry would confirm asthma on a child?
FEV1/FVC ratio < 0.8
What reversible airway obstruction would confirm asthma?
- Bronchodilator reversibility >12%
What Exhaled nitric oxide (FeNO) would confirm asthma on an adult?
Fraction of exhaled nitric oxide (FeNO): a non-invasive biomarker of airway (type-2) inflammation
More than 40ppb
What Exhaled nitric oxide (FeNO) would confirm asthma on a child?
Fraction of exhaled nitric oxide (FeNO): a non-invasive biomarker of airway (type-2) inflammation
More than 35ppb
Fraction of exhaled nitric oxide (FeNO): a non-invasive biomarker of airway (type-2) inflammation. How does Type 2 inflammation relate to asthma?
- Type 2 inflammation lead to eosinophilia
What FBC abnormality would one expect in a patient with asthma?
Blood eosinophil count: >300 cells/mcl
* Eosinophilia
Why would one need an need an FBC or more than one non-invasive biomarkers to diagnose asthma?
- A single non-invasive biomarker does not reflect airway eosinophilic inflammation
What are the management principles of asthma (3)?
- Reduce airway eosinophilic inflammation
- Acute symptomatic relief
- Severe asthma - steroid sparing therapies
How does one manage asthma (reduce airway eosinophilic inflammation) (2)?
- Inhaled corticosteroids (ICS)
- Leukotriene receptor antagonists
How does one manage asthma (acute symptomatic relief) (2)?
- Beta-2 agonists (smooth muscle relaxation)
- Anticholinergic therapies (smooth muscle relaxation)
How does one manage asthma (severe asthma) (3)?
- Biologic targeted to IgE
- Anti-IgE antibody (Omalizumab)
- Biologics targeted to airway eosinophils
- Anti-interleukin-5 antibody
- Anti-interleukin-5 receptor antibody
When is the use of omalizumab (anti-IgE antibody) recommended?
-
Severe, persistent allergic (IgE mediated) asthma in patients > 6 years who need continuous or frequent treatment with oral corticosteroids
- 4 or more courses in the previous year
Patient needs to have documented compliance bcs omalizumab is VERY expensive
What determines the dosage of omalizumab (anti-IgE antibody)?
Dosing based on:
* Total serum IgE (30-1500 IU/ml)
* Weight
Administered every 2-4 weeks subcutaneously
When is mepolizumab (anti-IL-5-antibody) recommended?
For severe eosinophilic asthma
* Blood eosinophils >300 cells/mcl in the last 12 months
* At least 4 exacerbations requiring oral steroids in the last 12 months
* Licenced for adults and children > 6 years
THEN
Trial for 12 months – 50% reduction in attacks, then continue
Outline the pathogenesis of an acute asthma attack.
