An asthma test is a diagnostic procedure administered to discount or confirm an asthma diagnosis. A variety of tests are utilized to evaluate an individual’s lung function, determine triggers associated with symptom onset, and evaluate disease severity. Instructions accompany the administration of an asthma test, are test-specific, and should be discussed with a qualified health care professional prior to testing. An individual may undergo more than one asthma test in order to confirm a positive diagnosis.
Generally, lung function tests are conducted in conjunction with the administration of a bronchodilator prior to and following testing. As a rule, if the individual’s lung function improves with the use of a bronchodilator, then he or she is likely asthmatic. Lung function tests include spirometry, peak flow, and a methacholine challenge test.
Spirometry assesses an individual’s lung function by measuring lung volume. During a spirometry test, an individual is instructed to take a deep breath and exhale forcefully into a tube attached to a spirometer. Two key measurements are registered as the spirometer measures the amount of air inhaled, exhaled, and the duration of exhalation. Forced vital capacity (FVC) is the quantity of air exhaled and forced expiratory volume (FEV-1) is the amount of air the individual expels from his or her lungs per second. A fraction of the two measurements is calculated and a percentage that falls below average is indicative of impaired lung function.
Peak flow measurement is an asthma test that allows the individual to monitor his or her triggers prior to an asthma attack. A simple device, the peak flow meter can be carried by the individual to be used outside the doctor’s office in order to track symptom onset and frequency. The meter detects the subtle changes in an individual’s breathing pattern prior to the onset of symptoms. Consistently low readings on a peak flow meter are indicative of asthma.
The methacholine challenge is an asthma test that involves the administration of an asthma trigger. Designed to utilize a known trigger, methacholine, in the presence of asthma, this test will induce mild airway constriction prompting symptom onset. A positive response to this exam is used to further substantiate an asthma diagnosis.
A nitric oxide test is administered to measure the amount of nitric oxide in an individual’s breath. If levels of nitric oxide are higher than normal, an individual’s airways may become inflamed, causing constriction and breathing difficulty. The test involves the individual breathing into a mouthpiece attached to a machine that measures nitric oxide levels. Considered a relatively new testing procedure, the nitric oxide test is generally administered with other tests, including spirometry and peak flow measurement.
Some asthma tests are used to substantiate a positive diagnosis while determining the presence of a secondary condition, such as an allergy or sinusitis. A blood test is employed to measure key antibody levels that increase in quantity during an allergic reaction. Allergy tests are administered as an evaluation tool to determine the presence of allergens, such as mold spores or pollen, which may be contributing to an individual’s asthmatic symptoms. Chest x-rays are generally conducted to verify there is no secondary condition that could be contributing to the individual’s symptoms. Due to complications associated with sinusitis, an evaluation of the individual’s sinuses is commonly conducted to rule out infection or nasal polyps which can impede asthma treatment.