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How is asthma diagnosed?
The International Consensus Report
describes asthma as "A chronic inflammatory disease of airways,
in susceptible individuals, inflammatory symptoms are usually
associated with widespread but variable airflow obstruction and
an increase in airway response to various stimuli. Obstruction
is often reversible, either spontaneous or with treatment."
The diagnosis of asthma is based on the patient's medical history, physical examination, and laboratory test results. To establish
a diagnosis of asthma, the clinician should determine that:
Episodic symptoms of airflow obstruction or airway
hyper responsiveness are present.
Airflow obstruction is at least partially reversible.
Alternative diagnoses are excluded.
Recommended methods to establish the diagnosis of asthma are:
Detailed medical history.
Physical examination focusing on the upper respiratory tract, chest,
and skin.
Look what triggers the asthma symptoms or when the
asthma symptoms get worse.
Investigations like
Spirometry to demonstrate obstruction and assess
reversibility, including in children 5 years of age or
older. Significant reversibility is indicated by an increase of
> 12 percent and 200 mL in FEV1 after inhaling a short-acting
bronchodilator (American Thoracic Society 1991). A 2 to 3 week
trial of oral corticosteroid therapy may be required to
demonstrate reversibility.
Family history of allergies or asthma.
Additional studies as necessary to exclude alternate
diagnoses.
Differential diagnosis of asthma:
INFANT AND
CHILDREN:
Upper airway diseases
- Allergic rhinitis and sinusitis
.
Obstructions involving large airways
- Foreign body in trachea or bronchus.
- Vocal cord dysfunction.
- Vascular rings or laryngeal webs.
- Laryngotracheomalacia, tracheal stenosis, or bronchostenosis.
- Enlarged lymph nodes or tumor
.
Obstructions involving small airways
- Viral bronchiolitis or obliterative bronchiolitis.
- Cystic fibrosis.
- Bronchopulmonary dysplasia.
- Heart disease
.
Other causes
- Recurrent cough not due to asthma.
- Aspiration from swallowing mechanism dysfunction or gastroesophageal reflux
.
ADULT:
- COPD (e.g., chronic bronchitis or emphysema).
- Congestive heart failure.
- Pulmonary embolism.
- Mechanical obstruction of the airways (benign and malignant tumors).
- Pulmonary infiltration with eosinophilia.
- Cough secondary to drugs (e.g., angiotensin-converting enzyme (ACE) inhibitors).
-
Vocal cord dysfunction
.
Medical
history:
-
Doctors ask
about the family history of asthma, allergies including
allergic rhinitis, eczema.
-
Children who
have family history of allergies, asthma have greater chances
of having asthma.
-
History of
recurrent and persistent cough and cold following exposure to
cold air, changing seasons.
-
Exercise limited
by breathing problem and wheezing
-
Occupational
history for exposure to gases, fumes, chemicals etc.
-
Any history of
emergency room visits or hospitalization following breathing
problem.
-
In the children
diagnosis is mainly clinical. Doctor determines when the
parents first noticed child developing breathing problem,
itchy eyes, nasal stiffness, eczema.
Asthma diagnosis is
suspected in all adult and children whose have following sign
and symptoms:
-
Recurrent Wheeze
which is a high-pitched whistling sounds when breathing
out—especially in children. (Lack of wheezing and a normal
chest examination do not exclude asthma.)
-
Cough, worse particularly at
night
-
Recurrent
breathlessness or difficulty in breathing
-
Recurrent
chest tightness
-
Recurrent lower
respiratory tract infections (LRTI)
-
Exercise induced cough/wheeze
Physical
examination:
Physical
examination includes listening to breath sounds over the chest
for possible ronchi or wheeze or rales, examination of nasal passage for evidence
of allergic rhinitis like nasal polyps and deviated nasal
septum.
Peak flow
meter:
Peak flow meter is a small portable hand held instrument used to
measure peak flow rates, or how well the airways are open.
Asthma is suspected when there is more than 20% diurnal
variation on 3 days or more in a week or for 2 weeks in a PEF
diary.
For more information click
Peak Flow Meter.
Lung function testing (Spirometry):
If symptoms and the patients history points towards the
diagnosis of asthma, the physician will perform spirometry to
confirm the diagnosis of asthma.
Spirometer is used to access the airflow obstruction. For
asthma diagnosis airflow obstruction should be at least
partially reversible.
To establish airflow obstruction physician uses spirometer to
measure (FEV1, FVC, FEV1/FVC) before and after the patient
inhales a short-acting bronchodilator.
For Obstruction to be present:
1. FEV1 should be
less than 80 percent predicted.
2. FEV1/FVC should
be 70 percent or below the lower limit of normal.
Establish
reversibility: FEV1
increases 12 percent or more and at least 200
ml after using a short-acting inhaled beta2-agonist (e.g., albuterol, terbutaline).
NOTE: Older adults
may need to take oral steroids for 2 to 3 weeks and then take
the spirometry test to measure the degree of reversibility
achieved.
Spirometry is
generally valuable in children over age 4; however, some
children cannot conduct the maneuver adequately until after age
7.
Challenge
tests:
If there are no
signs of airflow obstruction and asthma is still suspected, the
doctor may perform a challenge test by administrating histamine
or methacholine (a substance which causes airways to contract in
asthmatic individual), or may perform exercise challenge test.
These tests are used mainly in clinical laboratories to evaluate
airway hyper responsiveness.
A trial use of
asthma medication:
If asthma
medications are taken and there is improvement in the symptoms,
this further supports the diagnosis of asthma.
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Last edited 20-7-2010
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