Diagnosis of asthma  



Diagnosis of asthma







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:

    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
    • .


    • 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.


    Last edited 20-7-2010

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