Unlike asthma, COPD patients do not have normal lung function on a good day. The risk if you perform pre-bronchodilator diagnostic spirometry on your patients and the result is abnormal:

• it could be COPD
• it could also be asthma

If you perform post-bronchodilator diagnostic spirometry on your patients and the result is abnormal:

• it is COPD

Spirometry is still underused when a patient presents with signs and symptoms of COPD. However, the diagnostic accuracy of making COPD diagnosis just based on clinical findings, is around 50%.