Chronic obstructive pulmonary disease (COPD) is classified into one of four stages depending on test results that show the extent of damage to the lungs. Finding out the stage of COPD is important because it helps the doctor decide which treatments will be most effective. Knowing the stage at diagnosis also helps the doctor track how the disease is progressing as time goes on and whether treatments need to be changed.
There are two main approaches for diagnosing stages of COPD.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) system is based on only one measurement – forced expiratory volume (FEV1), which assesses the amount of air exhaled through a spirometer in a one-second interval. FEV1 compares your score to the score of a person similar in age, gender, and size with normal, healthy lungs to express a percentage of lung function.
The BODE Index takes several measurements into account in an effort to assess the impact of COPD on your life and predict estimated life expectancy. In the BODE approach, the doctor measures body mass index (BMI), pulmonary function, oxygen levels, and performance on a six-minute walking test. Learn more about tests used to diagnose COPD.
Depending on test results, you will be diagnosed with stage 1, 2, 3, or 4. Later stages have more severe symptoms and lower quality of life.
Stage 1 COPD is mild. Many people in stage 1 do not realize they have COPD. The most common symptoms are a cough with phlegm. According to the GOLD system, people with stage 1 COPD usually have approximately 80 percent of normal lung function.
Stage 2 COPD is moderate. People are more likely to see their doctor at this stage due to increased cough and phlegm production. Most people start taking medication at this stage. Based on the GOLD system, people with stage 2 COPD usually have 50 to 70 percent of normal lung function.
Stage 3 COPD is severe. At this stage, most people have trouble breathing and feel extreme fatigue. COPD begins to impact the quality of life and make daily activities difficult. Additional medications become necessary. The GOLD system defines stage 3 as 30 to 49 percent of normal lung function.
Stage 4, or end-stage COPD, is very severe. In end-stage COPD, most people have trouble getting enough oxygen. Quality of life is significantly impacted, and flare-ups can be life-threatening. Oxygen therapy usually becomes necessary. As expressed by the GOLD system, stage 4 COPD includes those with less than 30 percent of normal lung function remaining.
How does lung function percentage correlate with COPD stages?
Later stages of COPD generally correlate with lower lung function scores. One method of measuring COPD stages, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) system, is based on only one measurement – forced expiratory volume (FEV1). FEV1 measurement predicts the percentage difference between your score and the score of a similar person with healthy, normal lung function. However, the BODE Index stages COPD based on FEV1 score as well as several other measurements that assess overall health and physical function.
At what stage can you go on disability?
In the U.S., severe COPD that makes it difficult or impossible to work may qualify for social security benefits. In order to apply for benefits, it is necessary to provide several types of medical evidence including spirometry results to measure lung function, pulse oximetry and arterial blood gas tests to show how much oxygen is in your blood, as well as doctor’s notes and emergency room visit records relating to your COPD. Evidence will be required even if you take supplemental oxygen. Ask your doctor for help in understanding medical eligibility requirements.