Latest Classification of COPD
The latest classification of COPD uses a multidimensional approach that combines symptom burden, airflow limitation severity, and exacerbation history to create four patient groups (A, B, C, and D) to guide treatment decisions, with spirometric grades (1-4) assessed separately from symptoms and exacerbation risk. 1
Spirometric Classification
The spirometric classification of COPD severity includes:
| Grade | Severity | Post-bronchodilator FEV1/FVC | FEV1 % predicted |
|---|---|---|---|
| 1 | Mild | <0.70 | ≥80% |
| 2 | Moderate | <0.70 | 50-79% |
| 3 | Severe | <0.70 | 30-49% |
| 4 | Very Severe | <0.70 | <30% |
This classification is based on post-bronchodilator FEV1/FVC ratio <0.70, which confirms the presence of persistent airflow limitation 2, 1.
Symptom and Risk Assessment
The GOLD 2017 update made a significant change by separating spirometric assessment from symptom evaluation 2. Patients are now categorized based on:
Symptom burden - assessed using:
- Modified Medical Research Council (mMRC) Dyspnea Scale (≥2 indicates high symptoms)
- COPD Assessment Test (CAT) score (≥10 indicates high symptoms)
Exacerbation risk - based on:
- History of exacerbations (≥2 per year or ≥1 hospitalization indicates high risk)
ABCD Assessment Tool
The ABCD groups are now derived exclusively from patient symptoms and exacerbation history 2:
- Group A: Low symptoms (mMRC 0-1 or CAT <10) and low risk (<2 exacerbations, no hospitalizations)
- Group B: High symptoms (mMRC ≥2 or CAT ≥10) and low risk (<2 exacerbations, no hospitalizations)
- Group C: Low symptoms (mMRC 0-1 or CAT <10) and high risk (≥2 exacerbations or ≥1 hospitalization)
- Group D: High symptoms (mMRC ≥2 or CAT ≥10) and high risk (≥2 exacerbations or ≥1 hospitalization)
This revised classification has significantly changed the distribution of patients across groups, with Group B becoming more prevalent and Groups C and D decreasing in size 3, 4.
Composite Prognostic Indices
Several composite indices are used to assess prognosis in COPD:
- BODE index: Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity
- mBODE: Modified BODE using peak oxygen consumption instead of 6-minute walk distance
- BODEx: Replaces exercise capacity with exacerbation history
- ADO: Age, Dyspnea, and airflow Obstruction
- DOSE: Dyspnea, Obstruction, Smoking status, and Exacerbation frequency
- CODEx: Comorbidity, Obstruction, Dyspnea, and previous severe Exacerbations 2
Clinical Implications of the New Classification
The 2017/2018 GOLD update has several important implications:
Treatment decisions are now based exclusively on symptoms and exacerbation history, not on spirometric values 2
Group B patients now include many who were previously classified as Group D, making this group more heterogeneous with a higher risk of exacerbation compared to the previous classification 3
Group C is very small in most populations, reflecting the uncommon combination of few symptoms but high exacerbation risk 5, 6
Mortality patterns show Group A has the lowest mortality, Group D the highest, while Groups B and C have intermediate and surprisingly similar mortality rates 6
Limitations and Controversies
Several issues with the classification system have been identified:
Discordance between symptom measures: The assumed equivalence between mMRC ≥2 and CAT ≥10 has been questioned, with studies suggesting a CAT score of 17 might better correspond to mMRC ≥2 7
Discordance in exacerbation risk assessment: There is poor agreement between the two criteria for exacerbation risk (spirometry stage and exacerbation history) 7
Fixed ratio controversy: GOLD continues to use a fixed FEV1/FVC ratio of <0.70, while some experts recommend using the lower limit of normal (LLN) to avoid overdiagnosis in older patients 2, 1
Temporal stability: Patients classified as A or D tend to remain stable over time, while those in groups B or C change substantially during follow-up 6
The latest evidence suggests that including airflow limitation severity (creating 16 possible groups from 1A-4D) improves the prediction of respiratory mortality and hospitalization compared to the ABCD classification alone 4.
In clinical practice, this refined classification system helps guide treatment decisions while recognizing the heterogeneity of COPD and the importance of individualized assessment beyond just lung function measurements.