COPD vs Asthma Spirometry

COPD vs Asthma

	COPD	Asthma
Smoker	Almost all	Maybe
<35y	Rare	Often
Chronic productive cough	Common	Rare
Breathless	Persistent and progressive	Variable
Night time breathlessness or wheeze	Rare	Common
Day to day variation	Rare	Common
If any doubt, consider reversibility testing.

Spirometry

Restrictive pattern

Obstructive pattern

COPD
- FEV1/FVC < 0.7
- FEV1 < 80%
  - Mild 50-80%
  - Moderate 30-49%
  - Severe < 30%
- Reversibility test only if diagnostic doubt or asthma co-existing
  - COPD excluded if
    - FEV1/FVC & FEV1 returns normal after bronchodilator
  - Consider asthma if
    - Large (>400ml) FEV1 response to bronchodilator
Asthma
- High probability – Treatment and review
- Intermediate – Reversibility spirometry
  - FEV1/FVC < 0.7
  - FEV1 < 80%
  - Large (>400ml) FEV1 response to bronchodilator
- Low probability – Consider alternative diagnosis [reconsider diagnosis if other causes excluded]
- PEFR logs
  - >60 l/min is significant reversibility
  - Look for daily or diurnal variations
  - > 20% variation is of significance