|
For Obstruction to be present:
1. FEV1 should be
less than 80 percent predicted
2. FEV1/FVC should
be 70 percent or below the lower limit of normal.
Establish
reversibility:
FEV1 increases equal to or more than 12 percent and at least 200
ml after using a short-acting inhaled beta2-agonist (e.g.,
albuterol, terbutaline).
NOTE: Older adults
may need to take oral steroids for 2 to 3 weeks and then take
the spirometry test to measure the degree of reversibility
achieved.
Spirometry is
generally valuable in children over age 4; however, some
children cannot conduct the maneuver adequately until after age
7.
Challenge
tests:
If there are no
signs of airflow obstruction and asthma is still suspected, the
doctor may perform a challenge test by administrating histamine
or methacholine (a substance which causes airways to contract in
asthmatic individual), or may perform exercise challenge test.
These tests are used mainly in clinical laboratories to evaluate
airway hyper responsiveness.
A trial use of
asthma medication:
If asthma
medications are taken and there is improvement in the symptoms,
this further supports the diagnosis of asthma.
NEXT PAGE
Back to top |
