Diagnostic Read code for COPD

Age ≥35 years

Spirometry recorded between 3 months before and 12 months after the first COPD diagnostic code (index date)

Evidence of obstruction ever recorded (FEV₁/FVC<0.7)

Mild to moderate airflow limitation (FEV₁ % predicted ≥50% and ≤90% at index date)

≥1 year of up-to-standard* medical records prior to index date to enable baseline characterisation

History of smoking tobacco prior to first COPD diagnosis or at first recording after diagnosis

Height at adult age (≥21 years) and weight recorded within 5 years of index date

Up-to-standard* follow-up period covering ≥3 years between the first and last spirometry records

Active asthma at or after the date of first COPD diagnosis, defined as ≥1 diagnostic Read code for asthma or ≥1 asthma monitoring or review codes recorded, or asthma-COPD overlap syndrome as first COPD diagnostic code or recorded during follow-up

Diagnostic code for other chronic lower respiratory conditions ever recorded

Severe airflow limitation (FEV₁ % predicted <50% at index date) as there is limited scope for further FEV₁ decline and early intervention in these patients