Chronic obstructive pulmonary disease (COPD) is a progressive and debilitating respiratory illness with a poor prognosis and a reduced life expectancy. It is a disease caused by the presence of both chronic bronchitis and emphysema. The pathophysiological changes and symptoms of both these diseases signify COPD.
Early COPD diagnosis with spirometry, blood tests, chest x-ray, and CT scan becomes important in view of the potential complications and reduced life expectancy.
Spirometry with its results showing the FEV1/FEV ratio is also a very important parameter to diagnose COPD.
COPD diagnosis: Guidelines and criteria
There are fixed guidelines that serve as criteria in the diagnostic approach to COPD. These include:
- History taking
- Clinical assessment
- Blood tests
- Imaging studies, which involve chest x-ray and CT scan
History and clinical assessment
COPD diagnosis begins with the history of the patient. Before going in for blood tests and x-ray testing, your doctor will first want to know whether you are exposed to any risk factors, which can potentially make you a COPD patient. He will particularly delve into the following:
- history of your lifestyle habits – whether you smoke, how much you smoke, and for how long
- living environment – is it a polluted environment?
- your age
- family history – a family history of COPD is a risk factor
- presenting symptoms
Evaluating risk factors
- Age. COPD is a disease in adults. You will probably never see it in children. After significant lung damage has taken place, the symptoms first appear after the age of 35 to 40 years usually in the form of a cough with or without mucus. COPD is a lung disease in adults and the elderly.
- Smoking. Smoking is the most common and leading cause of COPD. About 90% of COPD cases are people who are or were smokers. Again, about 20% to 30% of chronic smokers eventually develop this lung disease. Cigarette smoke contains harmful toxins that over time cause damage to the lungs. Read about the pathophysiological changes that take place in the lung tissues in people who develop this disease.
- Living environment. You may be living in an industrial area where you are constantly exposed to air polluted with dust, chemicals, and other toxins emitted by the factories around you.
- Exposure to biogas smoke. Are you exposed to smoking wood used for cooking in poorly ventilated kitchens? Chronic and long-term exposure to such smoke is a potential cause.
Clinical assessment of the COPD patient
This involves the physical examination of the patient, which does not tell the doctor much in mild COPD cases.
The doctor will hear wheezing sounds and crackles on applying the stethoscope to the chest. These may be absent in severe cases when the patient is stable and on bronchodilator drugs.
Severe cases will show a barrel-shaped chest ( a hallmark of advanced emphysema), hyperinflated lungs, hyper-resonant sounds on percussion, and reduced movement of the chest wall.
He will then pack you off to the laboratory and the radiography department for you to undergo certain tests.
- spirometry test (also called lung function or pulmonary test)
- blood tests especially to detect Alpha-1 Antitrypsin Deficiency
- chest X-ray
- CT scan of your chest
The final diagnosis will come after excluding the differential diagnosis
Spirometry, also known as the lung function test or the pulmonary function test, measures the amount of air you can inhale and exhale. The results tell if your lungs are functioning properly, whether a proper gas exchange is taking place in the alveoli of the lungs, and delivering an adequate amount of oxygen to the blood.
It is used in the diagnosis of lung conditions such as asthma and COPD. The spirometer is a small testing device used in the office and the breathing test results are obtained in ten minutes.
It forms a definitive test in COPD diagnosis. It also helps to track the progression of the disease and to monitor the effect of the treatment.
For example, the doctor gives bronchodilator drugs to improve the breathing of the patient; spirometry results will tell him whether the medicines are working and have improved the breathing.
Interpretation of spirometry test results. Forced vital capacity (FVC), is the amount of air you can forcibly exhale from the lungs after taking the deepest breath possible. Forced expiratory volume (FEV1) is the amount of air you can blow out with full force in one second.
FEV1 – 80% to 120%
FVC – 80% to 120%
Absolute FEV1 /FVC ratio – 80%
Because of airflow obstruction or limitation, COPD patients take a longer time to blow the air out. The COPD pulmonary function test findings, therefore, show decreased values. An FEV1 with less than 70% of FVC can confirm the diagnosis of COPD in someone with correlating symptoms and history.
The FEV1/FEV ratio represents the proportion of a person’s total vital capacity that he can expire in the first second of forced expiration. The FEV1/FEV ratio helps to diagnose COPD and identify its stages per GOLD classification.
Most COPD patients typically visit their doctor when their lung function has fallen to 50% and sometimes much lower. It is, therefore, advised that the spirometry test become a part of all routine health checkup schemes in adults with a history of smoking.
A pulse oximeter measures the oxygen saturation in the blood. In COPD, due to lung damage, gas exchange is impaired, due to which blood oxygen levels fall and carbon dioxide levels rise.
The pulse oximeter is a useful device to find out the oxygen levels, especially when the patient is on oxygen therapy. The O2 levels will help the doctor to titrate the right oxygen dose for the patient.
Arterial blood gas (ABG) analysis
Arterial blood gas analysis also called the blood gas test is a laboratory blood test wherein the blood taken from the arteries is measured for levels of certain gases like oxygen and carbon dioxide. Usually, laboratory tests are done on blood taken from the veins.
ABG helps to determine the levels of oxygen and carbon dioxide in the arterial blood before it reaches the body tissues. The blood test results tell how well your lungs are functioning and whether a proper gas exchange, vis-a-vis oxygen against carbon dioxide, is taking place.
ABG is also used for other diagnostic purposes such as finding the pH of the blood and bicarbonate levels.
It is preferred over the pulse oximeter because the oximeter values are not always absolutely accurate in certain conditions. In such cases, the ABG test takes preference when knowing the accurate values becomes necessary.
Secondly, the pulse oximeter cannot detect blood acidosis (low pH levels) and hypercapnia (high CO2 levels).
Other blood tests: CBC and ABG
Other blood tests include the complete blood count (CBC) and the basic chemistry profile.
The complete blood count results will tell of the status of the cells in the blood. For example, a high white blood count will indicate that there is an infection. This test will also help to detect anemia and polycythemia.
Anemia is a deficiency of red cells or of hemoglobin in the blood and polycythemia is an abnormally increased concentration of hemoglobin in the blood, either due to a reduction of plasma volume or an increase in red blood cell numbers, which can occur in respiratory disorder such as COPD.
The basic chemistry profile includes the blood values of serum electrolyte levels, glucose, blood urea nitrogen, and serum creatinine. Electrolytes include sodium, potassium, chloride, and bicarbonate.
The purpose of doing the basic chemistry blood profile is to assess the functioning of the kidneys, liver, heart, adrenal glands, the endocrine system, and neuromuscular transmission.
Certain COPD complications and medications can alter the levels of the above-mentioned values, which can have serious consequences on the body organs, nerves, and muscles. Your doctor will, therefore, order these blood tests periodically.
Health communities gives an idea of the importance of detecting these abnormal values.
COPD genetic test
You may be genetically deficient in a protein called Alpha-1-antitrypsin, which is manufactured in the liver and protects the lungs. The deficiency of this protein increases your risk of COPD.
Alpha-1-antitrypsin deficiency is the most common hereditary disease among the white population. About 1 to 5% of diagnosed COPD cases are Alpha-1-antitrypsin deficient. Therefore, a blood test is carried out to screen the patients for this deficiency.
X-ray tests to diagnose COPD: chest x-ray and HRCT
Though spirometry is a useful tool to help diagnose COPD, it cannot readily differentiate the set of causes. It, therefore, has limited utility for treatment purposes. This is where imaging studies fill the gap.
- Chest x-ray. A chest x-ray will not help to diagnose COPD until it is severe. The x-ray findings will show enlarged lungs, irregular air pockets, or a flattened diaphragm, which are the tell-tale signs of COPD. However, it lacks the sensitivity to detect both airway disease and mild emphysema, and therefore, a CT or CAT scan becomes necessary for an in-depth analysis.
- Computed tomography (CT scan). In COPD, a CT scan attains importance particularly to identify other potential causes for symptoms of cough or breathlessness. Other lung conditions such as chronic lung infections, bronchiectasis, lung fibrosis, and lung cancer can mimic these symptoms. CT helps to differentiate these lung conditions. CT is particularly important in patients with COPD who experience a change in their symptoms. In severe COPD cases, CT helps in the indication of a surgical option along with identifying the part of the lung suitable for resection.
- High-resolution computed tomography (HRCT). A high-resolution computed tomography (HRCT) scan of the chest is a CT scan with high-resolution images. It can detect emphysema even in people whose lung function or chest x-ray is normal. As compared to an ordinary CT, it has a sensitivity of 95 percent. A sure-shot COPD diagnosis is possible in approximately one-half of the cases with an accuracy of an estimated 93 percent.
Your doctor may order an ECG if he suspects the development of a heart condition such as cor pulmonale, a common complication of COPD.