COPD Classification Systems
COPD is classified using two complementary systems: spirometric severity based on post-bronchodilator FEV1 % predicted, and the GOLD ABCD assessment tool that incorporates symptom burden and exacerbation history to guide treatment decisions. 1
Diagnostic Confirmation Required First
Before classification, diagnosis must be confirmed with post-bronchodilator spirometry showing FEV1/FVC ratio ≤0.70, which defines persistent airflow limitation 2, 1, 3. This requires administering either 400 mcg salbutamol or 80 mcg ipratropium bromide before measurement 3.
For borderline cases with FEV1/FVC between 0.60-0.80, repeat spirometry within 3-6 months is recommended to account for day-to-day biological variability 1, 4.
Spirometric Classification by Airflow Obstruction Severity
Once obstruction is confirmed (FEV1/FVC ≤0.70), severity is stratified by post-bronchodilator FEV1 % predicted 2, 1, 3:
GOLD Spirometric Grades 2, 1, 3:
- GOLD 1 (Mild): FEV1 ≥80% predicted
- GOLD 2 (Moderate): FEV1 50-80% predicted
- GOLD 3 (Severe): FEV1 30-50% predicted
- GOLD 4 (Very Severe): FEV1 <30% predicted
Critical limitation: FEV1 alone correlates poorly with symptoms, fails to capture lung hyperinflation, and does not accurately predict clinical severity or prognosis for individual patients 3. This is why multidimensional assessment is essential.
GOLD ABCD Assessment Tool (Primary Classification for Treatment)
The GOLD ABCD system is the primary framework for treatment decisions, combining symptom burden with exacerbation history 2, 1:
Symptom Assessment 1, 4:
- Low symptoms: Modified Medical Research Council (mMRC) dyspnea scale <2 OR COPD Assessment Test (CAT) score <10
- High symptoms: mMRC ≥2 OR CAT ≥10
Exacerbation Risk 2, 1:
- Low risk: 0-1 exacerbations per year (not requiring hospitalization)
- High risk: ≥2 exacerbations per year OR ≥1 hospitalization for exacerbation
GOLD Groups 1:
- Group A: Low symptoms + Low exacerbation risk
- Group B: High symptoms + Low exacerbation risk
- Group C: Low symptoms + High exacerbation risk
- Group D: High symptoms + High exacerbation risk
Important note: The 2017 GOLD revision removed spirometry from the ABCD classification, causing approximately half of patients previously classified as GOLD D 2011 to shift to GOLD B 2017 5. This makes GOLD B 2017 more heterogeneous with higher exacerbation risk than the previous version 5.
Exacerbation Classification
COPD exacerbations are classified by treatment intensity 2, 1:
- Mild: Treated with short-acting bronchodilators only 2
- Moderate: Requires short-acting bronchodilators plus antibiotics and/or oral corticosteroids 2, 1
- Severe: Requires hospitalization or emergency room visit; may be associated with acute respiratory failure 2
Patients with ≥2 exacerbations per year are classified as "frequent exacerbators" and have worse health status, increased morbidity, and higher mortality risk 2.
Multidimensional Prognostic Indices
Several composite indices provide superior prognostic information compared to FEV1 alone 1, 3:
BODE Index (Most Validated) 3:
- Body mass index (BMI <21 kg/m² associated with increased mortality)
- Obstruction (FEV1 % predicted)
- Dyspnea (mMRC scale)
- Exercise capacity (6-minute walk distance)
Alternative Indices 3:
- ADO Index: Age, Dyspnea, Obstruction
- BODEx Index: Replaces exercise capacity with exacerbation rate
- DOSE, CODEx, mBODE: Other validated composite tools
These indices are particularly useful for prognostic stratification beyond treatment planning 1, 3.
Additional Assessment Parameters
Hyperinflation Assessment 3:
Inspiratory capacity (IC) measurement provides indirect assessment of hyperinflation and correlates more closely with dyspnea and exercise intolerance than FEV1 alone 3.
Comorbidity Screening 1, 4:
Actively screen for: lung cancer, cardiovascular diseases, metabolic syndrome, diabetes, osteoporosis, anxiety, and depression, as these significantly impact disease severity and prognosis 1, 4.
Common Pitfalls to Avoid
Do not rely solely on spirometry for treatment decisions 1. The spirometric grade (GOLD 1-4) identifies airflow obstruction severity but does not determine treatment intensity—use the ABCD assessment tool instead 1.
Do not assume GOLD B patients are low-risk 5. Following the 2017 revision, GOLD B includes many patients with moderate-to-severe airflow obstruction who were previously classified as GOLD D, making this group more heterogeneous with higher exacerbation rates 5.
Do not overlook the "at risk" category 2. Patients with FEV1/FVC >0.7 but exposure to pollutants and respiratory symptoms (cough, sputum, dyspnea) warrant monitoring even without confirmed COPD 2.