What tests are needed to diagnose asthma

Asthma is a very harmful disease. Although the symptoms are very obvious, a comprehensive examination is still needed to determine the condition when suspected symptoms appear. Like other diseases, the diagnosis of asthma requires many examination items. If you suspect that you have asthma, you can briefly understand the main examination methods. So, what tests are needed to diagnose asthma? Let’s take a look below.

examine

1. Physical examination

There may be no abnormal signs during the remission period. During the attack, the chest is bulging and the percussion sound is too clear. Most patients have widespread wheezing mainly in the expiratory phase, and exhalation is prolonged. Severe asthma attacks often include signs such as labored breathing, profuse sweating, cyanosis, abnormal chest and abdominal movements, increased heart rate, and pulsus paradoxus.

2. Laboratory and other tests

(1) Routine blood examination may show an increase in eosinophils during an attack, but in most cases it is not obvious. If there is a concurrent infection, the white blood cell count may increase and the proportion of classified neutrophils may increase.

(2) Sputum smear examination under a microscope shows a large number of eosinophils, sharp-edged crystals formed by the degeneration of eosinophils, mucus plugs and transparent asthma beads (Laennec beads). If combined with respiratory bacterial infection, sputum smear Gram staining, cell culture and drug sensitivity testing can help diagnose the pathogen and guide treatment.

(3) Pulmonary function tests show that lung ventilation function is mostly within the normal range during the remission period. During an asthma attack, due to limited expiratory flow rate, the forced expiratory volume in the first second, the one-second rate, the maximum mid-expiratory flow rate, the maximum expiratory flow when exhaling 50% and 75% of vital capacity, and the peak expiratory flow are all reduced. There may be a decrease in forced vital capacity, an increase in residual volume, functional residual capacity and total lung capacity, and an increase in the percentage of residual air in total lung capacity. It can gradually recover after treatment.

(4) Blood gas analysis: Severe asthma attacks may cause hypoxia, decreased PaO2 and SaO2. Hyperventilation may cause a decrease in PaCO2 and an increase in pH, indicating respiratory alkali poisoning. For example, in severe asthma, if the condition progresses further and the airway obstruction becomes severe, there may be hypoxia and CO2 retention, increased PaCO2, and respiratory acidosis. If hypoxia is obvious, metabolic acidosis may occur.

(5) Chest X-ray examination shows increased translucency of both lungs during an asthma attack, indicating hyperinflation; there are usually no obvious abnormalities during the remission period. If complicated with respiratory tract infection, increased lung texture and inflammatory infiltration shadows may be seen. At the same time, attention should be paid to the presence of complications such as atelectasis, pneumothorax or mediastinal emphysema.

(6) Specific allergens can be detected by measuring specific IgE using the radioactive allergen adsorption test. The serum IgE of patients with allergic asthma can be 2 to 6 times higher than that of normal people. During the remission period, skin allergy tests can be performed to identify related allergens, but allergic reactions should be prevented.

diagnosis

A clinical diagnosis can be made for typical symptoms and signs. For atypical cases, the following examinations should be performed, which can be combined with the response to treatment to confirm the diagnosis.