Diagnosing asthma

• History & Physical examination• Measurements of lung function– Spirometry– Peak expiratory flow

• Measurements of airway hyperresponsiveness– Inhaled metacholine/histamine (DIRECT)– Inhaled mannitol/exercise challenge (INDIRECT)

• Measurements of allergic status– Skin allergen test & IgE serum

HOST RISK FACTORS ENVIRONMENTAL RISK FACTORS

Genetics- Parental asthma- Predisposition to atopy- Predisposition to airway hyperresponsiveness

AllergensIndoor/outdoor

Obesity Infections (usually Viral)

Sex (male) Occupational sensitizers

Low birth weight Tobacco smoke

Outdoor/indoor air pollution

Diet

Diagnosing asthma - HISTORY

Diagnosing asthma - HISTORY

• Consider asthma if any of the ff. are present:– Frequent episodes of wheezing (>1x/month)– Activity induced cough or wheeze– Cough at night (during period w/o viral infection)– Absence of seasonal variation of wheeze– Symptoms persist after age 3

Diagnosing asthma - HISTORY

• Consider asthma if any of the ff. are present:• Symptoms occur or worsen in the presence of:

– Animals with fur, aerosol chemicals, changes in temp., domestic dust mites, drugs like aspirin and beta-blockers, exercise, pollen, respiratory viral infections, smoke, strong emotional expression

– The childs colds repeatedly “go to the chest” or take more than 10 days to clear up.

– Symptoms improve when asthma medication is given

Diagnosing asthma – ROS & PE

• Decreased physical activity• General fatigue, inability to sleep• Difficulty keeping up with peers in physical

activities• WHEEZING (may be absent if severe)• Breathlessness• Chest tightness• Cough (usually at night or early morning)

Diagnosing asthma – Lung Function Tests

1) Spirometry - preferred method of measuring airflow limitation and

its reversibility- Reversibility = increase in FEV1 of >= 12% or 200 mL

after administration of bronchodilator

Diagnosing asthma – Lung Function Tests

2) Peak Expiratory Flow (PEF)- PEF measurements are compared to patient’s own

best measurements using peak flow meter- Suggests asthma if:a) Improvement of 60 L/min or >= 20% of pre-

bronchodilator PEF after inhalation of a bronchodilator

b) Diurnal variation in PEF > 20% (with 2x daily readings more than 10%)

Diagnosing asthma – Measurements of airway hyperresponsiveness

• Direct/Indirect airway challenges• Helps in diagnosing asthma in patients with normal

lung function but has symptoms consistent with asthma

• Reflect sensitivity of airways to factors that can trigger asthma

• Expressed as the provocative concentration (or dose) of a given agonist causing a given fall in FEV1 (usually 20%)

• Sensitive but not specific

Diagnosing asthma – Measurements of allergic status

1) Skin test with allergen- Primary diagnostic tool - Simple, rapid to perform, low cost, high

senstivity

2) Serum IgE- More expensive

Diagnostic Challenge

• Diagnosing asthma in children < 5 years old is largely based on CLINICAL JUDGEMENT, SYMPTOMS, and PHYSICAL FINDINGS

• Confirm diagnosis by trial of treatment with bronchodilators & inhaled glucocorticoids– Improves with treatment– Deteriorates when treatment is stopped

Spirometry video

What causes asthma?

Controlling asthma attacks

bronchodilators