Saturday, May 25, 2013

Diagnosing Asthma in Children and Adolescents

Table of Contents

Diagnosis


Pulmonary Function Tests

If symptoms and a patient's history strongly suggest asthma, the doctor will usually perform tests called pulmonary function tests to confirm the diagnosis and determine the severity of the disease.

Using a spirometer, an instrument that measures the air taken into and exhaled from the lungs, the doctor will determine several values:

  • Vital capacity (VC), the maximum volume of air that can be inhaled or exhaled.
  • Peak expiratory flow rate (PEFR), commonly called the peak flow rate, the maximum flow rate that can be generated during a forced exhalation.
  • Forced expiratory volume (FEV1), the maximum volume of air expired in 1 second.

If the airways are obstructed, these measurements will fall. Depending on the results, the doctor will take the following steps:

  • If measurements fall, the doctor typically asks the patient to inhale a bronchodilator medication. This drug is used in asthma to open the air passages. The measurements are taken again. If the measurements are more normal, the drug has most likely cleared the airways, and a diagnosis of asthma is strongly suspected.
  • If measurement results fail to show airway obstruction, but asthma is still suspected, the doctor may perform a challenge test. It involves administering a specific drug (histamine or methacholine) that usually increases airway resistance only when asthma is present.

Allergy Tests

The patient may receive skin or blood allergy tests, particularly if a specific allergen is suspected and available for testing. Allergy skin tests help diagnose for allergic asthma, although they are not recommended for people with year-round asthma.

Allergy skin prick or scratch test
One of the most common methods of allergy testing is the scratch test or skin prick test. The test involves placing a small amount of the suspected allergy-causing substance (allergen) on the skin (usually the forearm, upper arm, or the back), then scratching or pricking the skin so that the allergen is introduced under the skin surface. The skin is observed closely for signs of a reaction, which usually includes swelling and redness of the site. With this test, several suspected allergens can be tested at the same time, and results are usually available within about 20 minutes.

Review Date: 05/03/2011
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)