Diagnosis of Asthma
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Asthma can be difficult to diagnose because the symptoms are sometimes similar to other lung conditions. Initially, your doctor will ask about your symptoms and medical history. A physical exam will be done.
In addition, the following tests may be performed:
]]>Chest x-ray]]> is the initial imaging test for most people with symptoms of asthma. A chest x-ray can reveal other causes of wheezing (other than asthma) or complications (such as ]]>pneumonia]]> ).
Pulmonary Function Tests (PFTs)
]]>Pulmonary function tests (PFTs)]]> is an instrument known as a spirometer is used to measure how much air is inhaled and expelled as you breathe. This test will measure both the amount and rate of air that can pass through your airways. The diagnosis of asthma is usually made when reversible lung airway obstruction is demonstrated on PFTs. A peak flow meter is used to measure the rate at which you expel air. Peak flow meters can also be used at home to assess the degree of airway obstruction, indicating an imminent asthma attack.
People with asthma will experience a mild constriction of the airways when the drug methacholine is inhaled. If asthma is suspected, but there are no obvious symptoms of airflow obstruction on PFTs, methacholine is administered and the tests are run again. Alternative provocation tests include administration of histamine or inhalation of cold air. The diagnosis of asthma is usually made if the PFTs indicate lung airway obstruction during a provocation tests.
You may have ]]>Allergy tests]]> if allergic asthma is suspected. A tiny allergen particle is placed under the skin with a needle. In 80% of cases, an allergic response is confirmed if the skin becomes raised or red within 20 minutes.
Peak Flow Meter
American College of Allergy, Asthma, & Immunology website. Available at: http://www.acaai.org/ . Accessed July, 2008.
American Lung Association website. Available at: http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=22542 . Accessed July, 2008.
Asthma. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated July 2009. Accessed July 21, 2009.
Braunwald E. Harrison's Principles of Internal Medicine . 15th ed. New York, NY: McGraw-Hill; 2001.
National Asthma Education and Prevention Program: Expert panel report III: Guidelines for the diagnosis and management of asthma. Bethesda, MD: National Heart, Lung, and Blood Institute, 2007. (NIH publication no. 08-4051). Full text available online: ]]>www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm]]> (Accessed September 1, 2007).
Last reviewed December 2009 by ]]>Marcin Chwistek, MD]]>
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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