About the Diagnosis of Asthma

1. Asthma Symptoms If any one of the following applies, you should consult a specialist.

(1) Coughing or wheezing occurs and does not go away easily, and happens repeatedly. (2) On cold days or windy days, the chest feels tight, wheezing appears, and coughing occurs. (3) After having a cold, coughing continues for more than a month. (4) While sleeping at night, you have woken up because of severe coughing or shortness of breath. (5) After smelling cigarette smoke, exhaust fumes, or similar irritants, the chest felt tight, shortness of breath occurred, or coughing became severe. (6) After taking cold medicine, breathing became labored and painful.

2. Asthma Tests The tests performed for the diagnosis and treatment of asthma include the following.

[Tests performed to confirm whether asthma is present] · Pulmonary function test   · Bronchial provocation test

[Tests performed to find the cause of asthma] · Allergen skin prick test   · Blood specific immunoglobulin E test   · Allergen provocation test

[Tests performed to check for other respiratory diseases] · Chest X-ray   · Sputum test   · Bronchoscopy

1. Pulmonary Function Test A pulmonary function test evaluates the overall function of the lungs by mechanically recording the patient’s breathing and displaying it as a graph. Among the various indicators in pulmonary function testing, the especially important ones for patients with asthma are 'Peak Expiratory Flow Rate (PEFR)' and 'Forced Expiratory Volume in 1 second (FEV1)'.

[Peak Expiratory Flow Rate (PEFR)] In Sino-Korean terms, inhaling is called 'inspiration' and exhaling is called 'expiration'. When asthma occurs, the bronchi narrow, making exhalation difficult. Therefore, if the speed of the patient’s exhaled breath (expiratory flow rate) is measured, it can be confirmed that it is significantly reduced compared with normal.

[Forced Expiratory Volume in 1 second (FEV1)] Under normal conditions, human breathing is characterized by inhalation being relatively short and exhalation being long. Also, when exhaling, a large amount of air comes out quickly at first, and then the remaining air comes out gradually, so the pattern looks like the graph below. On the other hand, in patients with asthma, the airways are narrowed, so the speed of airflow during exhalation drops significantly. Therefore, even when exhaling with great effort, the amount of air exhaled in one second (expiratory volume) is greatly reduced compared with that of a healthy person.

[Bronchial Provocation Test] To assess the presence and degree of bronchial hyperresponsiveness, which is characteristically seen in patients with asthma, a bronchial provocation test using methacholine is performed.

Methacholine is inhaled in aerosol form, starting from a low concentration and gradually increasing to a high concentration. After that, lung function is measured. If the forced expiratory volume in 1 second (FEV1) decreases by 20% or more compared with before inhalation, bronchial hyperresponsiveness is diagnosed. When the decrease exceeds 20%, a bronchodilator is inhaled, and the changes in forced expiratory volume in 1 second (FEV1) are observed 5 and 10 minutes later. The degree of bronchial hyperresponsiveness is evaluated based on the decreased FEV1 value.

2. Allergen Skin Prick Test This test is used to identify the allergen that causes the allergy. For the skin prick test, drops of medications (allergen extracts) containing various substances that cause allergic diseases are placed one by one on the patient’s back, and then the area is lightly pricked with a needle so that the allergen solution reaches the epidermis. After about 15 to 30 minutes, when the skin reaction caused by the allergen reaches its peak, measuring the degree of the skin reaction can help identify the causative substance that triggers asthma. For an accurate test, medications such as antihistamines and antidepressants should be stopped at least 3 days in advance.

3. Chronic Cough Test Using Capsaicin This test measures cough sensitivity to external stimuli. Capsaicin is one of the components of chili peppers and is known to trigger coughing. By inhaling capsaicin, the patient’s cough sensitivity is measured. If cough sensitivity is increased, coughing can be triggered even by very low concentrations of stimulus. In some patients with chronic cough, the methacholine bronchial provocation test may be negative while only the capsaicin cough provocation test is positive, so capsaicin provocation testing is necessary for the diagnosis of chronic cough.

So far, I have explained the diagnosis of asthma. In the next part, we will look at the treatment of asthma.

Source: Korea Disease Control and Prevention Agency, National Health Information Portal