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Asthma Tests & Diagnosis

Doctor tests woman for asthmaThere are many people who have asthma, but this it is not diagnosed with just one single test.  Rather, there are several tests to run and factors to take into account when determining a proper diagnosis.  Some diagnostic tests determine lung function, blood tests analyze people’s overall health, and other tests determine allergies and whether or not there are any coexisting medical conditions.

(If you have been diagnosed with asthma, then you might qualify for our asthma clinical trial in Birmingham, AL)

Diagnostic testing for asthma includes the following tests:

  • Check-up with your doctor
  • Lung function tests
  • Spirometry
  • Methacholine challenge test
  • Peak expiratory flow rate
  • Chest X-ray
  • Allergy testing
  • Blood tests
  • Discovering coexisting medical conditions
  • Lung inflammation tests
  • Phlegm sampling
  • Nitric Oxide Concentration

Physical Check-Up:

Your doctor will listen to your breathing with a stethoscope and check your mouth and nose.  He may ask you about your profession, smoking habits and recreational activities to determine if any of these could be the cause or exacerbation of your asthma case.  If you come into close proximity of a factory, chemical fumes, paint, debris, dander, timber and other allergens, your asthma diagnosis may be attributable to these occupational culprits.  Painters, nurses, factory employers and bakers are some commonly diagnosed professionals with asthma.

Lung Function Tests:

To evaluate how well your lungs are functioning, your doctor may test your breathing.  The tests used for this are spirometry and methacholine challenge tests.  These two tests are the most commonly used lung function tests for asthma diagnosis.


The principle way to determine lung function is to evaluate any obstruction to the airflow in the lungs.  Two ways to do this is to measure the quantity of air exhaled in one second (forced expiratory volume, FEV1) and the total amount of air exhaled (the forced vital capacity, FVC).  This test is called spirometry and it is the most commonly used lung function test for asthma diagnosis and check ups.  You will breathe into a spirometer machine and the appropriate measurements will be taken.  You may be given a reliever inhaler to dilate your airways to see if it helps you with your breathing by breathing into the spirometer again after using the inhaler.

Methacholine Challenge Test:

If the spirometry does not provide convincingly accurate results, or if your symptoms and spirometry results do not match up, your doctor may perform a methacholine challenge test.  This test measures your lung responsiveness to asthma exacerbations.  You first exhale into a spirometer and have your FEV1 and FVC measurements recorded.  Then you will inhale histamine or methacholine to bring about asthma symptoms.  Once the asthma symptoms kick in, you will exhale into a spirometer and have your FEV1 and FVC measured.  If these levels are much lower than those recorded before your asthma symptoms were exacerbated, there is a high chance that you have asthma.

Peak Expiratory Flow Rate:

Another way to determine any obstruction to the airflow in the lungs is to measure how quickly you can exhale the air in your lungs in one breath (peak expiratory flow rate, PEFR).  You may be given a peak flow meter to take home with you so that you can determine when your asthma symptoms are triggered and your breathing is worsening.

Chest X-ray:

An X-ray takes images of the body through low radiation.  Lung X-ray imaging is used to detect lung damage caused by such medical conditions as bronchitis, emphysema, broken ribs and asthma.  Your doctor may prescribe a chest X-ray so that he can evaluate if the diagnosis of asthma fits your symptoms and the appearance of the condition of your heart, rib cage, bones and lungs.

Allergy Testing:

Asthma may be a result of allergic reactions to foods, asbestos, pollen, dander and other allergens.  Further testing may ensue to determine the cause of the allergy in order to prevent asthma attacks and better treat the resultant asthma.  Untreated allergies can severely worsen asthma, so it is important to identify allergies and treat them as needed.

Blood Tests:

Blood tests analyze patients’ general health.  Immunoglobulin E (IgE) is an important protein antibody that comes into play during an allergic reaction, and its levels may be tested in the process of diagnosing asthma.  Elevated levels of IgE are present in those with allergies, and allergies may be a coexisting medical condition and even the cause of asthma attacks.

Discovering Coexisting Medical Conditions:

Other common coexisting conditions with asthma include GERD (gastroesophageal reflux disease), heartburn, sinus polyps and sinusitis.  Your doctor may prescribe medications and treatments for the coexisting condition(s) in addition to your asthma if necessary.  In some cases, treating the other medical condition may put an end to asthma attacks altogether. In other cases, asthma is treated as a recurring chronic condition.  GERD and heartburn can rigorously worsen asthma if not treated.  In addition, sinus polyps may interfere with the success of asthma treatment, and sinusitis may severely exacerbate the condition of asthma if not treated with appropriate antibiotics.

Lung Inflammation Tests:

Asthma patients experience inflamed airways in the lungs, a sign of respiratory ailment and inadequate functioning.  The following two tests are ways to determine lung inflammation without using invasive testing.

Phlegm Sampling:

Lung inflammation can be detected in the phlegm coughed up by asthma patients, so your doctor may order a clinical sampling.

Nitric Oxide Concentration:

As part of exhalation, we expel nitric oxide from our bodies.  Lung inflammation can be detected by a high concentration of nitric oxide, so your doctor may order a clinical analysis of the concentration of nitric oxide in your exhalation breath.

It is important to diagnose asthma so that appropriate treatments may commence.  If left untreated, your asthma case may degenerate and becoming fatal.  Asthma can be treated, so talk to your doctor today about the appropriate diagnostic testing and treatment options for you.