GOLD Classification for COPD
The GOLD classification system uses two separate but complementary staging approaches: spirometric grades (1-4) based on FEV₁ severity, and ABCD groups (A-D) based exclusively on symptom burden and exacerbation history. 1
Spirometric Classification (Airflow Limitation Severity)
The spirometric staging requires post-bronchodilator FEV₁/FVC ratio <0.70 to confirm airflow limitation, then grades severity by FEV₁ percentage predicted: 1
- GOLD 1 (Mild): FEV₁ ≥80% predicted 1
- GOLD 2 (Moderate): FEV₁ 50-79% predicted 1
- GOLD 3 (Severe): FEV₁ 30-49% predicted 1
- GOLD 4 (Very Severe): FEV₁ <30% predicted 1
ABCD Assessment Groups (Symptom and Exacerbation-Based)
A critical 2017 revision separated spirometry from the ABCD grouping—these groups are now derived exclusively from symptoms and exacerbation history, not lung function. 1 This represents a fundamental shift from prior versions where spirometry influenced group assignment. 1
Group Assignment Algorithm:
Step 1: Assess Symptom Burden 1
- Low symptoms: mMRC 0-1 OR CAT <10
- High symptoms: mMRC ≥2 OR CAT ≥10
Step 2: Assess Exacerbation Risk 1
- Low risk: 0-1 exacerbations per year (not requiring hospitalization)
- High risk: ≥2 exacerbations per year OR ≥1 hospitalization for exacerbation
Step 3: Assign Group 1
- Group A: Low symptoms + Low risk
- Group B: High symptoms + Low risk
- Group C: Low symptoms + High risk
- Group D: High symptoms + High risk
Important Clinical Caveats:
Discordance between symptom assessment tools occurs frequently. 2 When mMRC and CAT disagree (22% of patients in one study), use whichever indicates higher symptom burden to avoid undertreatment. 2 The assumed equivalence of mMRC ≥2 and CAT ≥10 has poor specificity (24%), while CAT ≥17 has better specificity (98%) but lower sensitivity (52%). 2
Group C is clinically rare (4-12% of patients), as most patients with frequent exacerbations also have high symptom burden, placing them in Group D instead. 3, 4 This creates practical classification challenges for the minority with severe airflow obstruction but infrequent exacerbations, or mild obstruction with frequent exacerbations. 4
Spirometric severity does not reliably predict exacerbations or mortality within the same ABCD group. 5 Patients in Groups B and D tend to have worse spirometry than Groups A and C, but within each group, FEV₁ severity does not predict future exacerbation rates. 5 This validates the separation of spirometry from ABCD grouping for treatment decisions. 1
The exacerbation risk criteria show substantial disagreement (45% discordance, kappa 0.12) when comparing spirometric staging versus exacerbation history. 2 When these conflict, classify based on whichever criterion indicates higher risk. 1