Chronic obstructive pulmonary disease (COPD): coding considerations

Hospital discharge data

Unless otherwise specified, references in the data to 'COPD' refer to patients with COPD as classified by ICD10 codes J40 - J44 (including all their subsidiary codes) and, in some older data, ICD9 codes 490 - 492 and 496. It should be noted that the coding in the Scottish Morbidity Record (SMR01) changed from ICD9 to ICD10 between March and April 1996.

Mortality data

Mortality data are published by National Records of Scotland (formerly the General Register Office for Scotland) and use the same ICD10 codes as for hospital discharges. The transition from ICD9 to ICD10 occurred slightly earlier for mortality data than hospital discharge data, between December 1999 and January 2000. Comparisons of the two coding systems suggested a reasonable degree of comparability for COPD mortality. 

Primary care data

Clinical coding in primary care in Scotland is currently in transition from the Read coding system to SNOMED CT as part of the implementation of the Digital Health and Care Strategy 2021 and the Health and Social Care: Data Strategy 2023. Primary care statistics presented in this section are based on Public Health Scotland’s Read Code Grouping ‘Bronchitis, emphysema & other chronic obstructive pulmonary disease’ detailed below. More information on Read codes can be found on the PHS website.