COPD or Asthma?
Asthma and COPD both have similar symptoms and a differentiation of both diseases is not always easy. Since both diseases have to be treated in a different way, a careful diagnosis is important.
Both asthma and COPD show wheezing, shortness of breath, chest tightness and coughing, sputum, and use of accessory muscles as the dominant symptoms. Asthma is caused by environmental and genetic factors. These factors influence how severe asthma is and how well it responds to medication. The interaction is complex and not fully understood. Usually asthma is congenital. In contrast, COPD develops over time and is mainly caused by smoking and environmental pollutants.
In both COPD and asthma a spirometer can show a reduced PEF, FEV1 and FEV1%. A body plethysmography measurement can show an increased airway resistance and an increased residual volume (RV).
Important hints regarding the differentiation of both diseases can be delivered by the medical history of the patient. An important difference is that COPD is permanent and asthma occurs in a paroxysmal manner. However, if the subject suffers from severe asthma of severeness level 4 the symptoms are actually present all the time.
Signs of asthma are apparent in infants. In contrast, it is rare for people to have COPD before the age of 40. Furthermore, COPD starts mild and becomes more severe over time. Asthma is not necessarily related to smoking, but smoking can increase the symptoms and can cause an attack. COPD patients are usually smokers or people who are exposed to pollutants. Usually asthma causes less sputum than COPD. Additionally, asthma patients mainly cough at night, whereas COPD patients generally cough more in the morning.
A comparatively safe method for the differentiation is an inhalational provocation test or a bronchodilator test.
A bronchodilator test is performed during an acute obstruction. The patient exhales short-acting β-agonists such as salbutamol. If the patient suffers from asthma, the airways will expand and a performed spirometry test will show improved results. If the patient suffers from COPD, the symptoms will just slightly improve. If asthma is present, FEV1 should increase by at least 15%.
Another possibility could be the long-term inhalation of a steroid like cortisone. After 4 weeks the vast majority of the asthma patients should experience a minimisation of the symptoms, whereas just 10% of the COPD patients experience the same. These tests could at the same time evaluate if a therapy with salbutamol or cortisone could be a useful method of treatment.
The opposite method is applied with a provocation test. A medical drug, mostly histamine, irritates the bronchia. Patients suffering from asthma will experience shortness of breath, caused by a temporary obstruction. Especially FEV1 and PEF are observed in this case.
Another useful possibility could be diffusion testing. Patients suffering from COPD usually show a decreased TLCO or DLCO respectively. In contrast to that a recent study has shown that patients suffering from asthma usually have an increased TLCO or DLCO respectively (in 62% of the subjects).
If the symptoms are mostly present under exercise an ergospirometry test should be carried out.
Other possibilities could be x-ray of the chest and the examination of the sputum. X-rays of asthma patients are usually normal. COPD patients often show first signs of emphysema. In the cells of asthmatic sputum eosinophil granulocytes will dominate, whereas in the case of COPD neutrophil granulocytes will be the dominant cells.
Bronchial dosimeter for carrying out bronchodilator and provocation tests