What is the difference between ICD 9 and ICD 10 data?

UK Biobank (UKB) receives linked health-related outcomes data from the Cancer Registry, NHS Digital (Hospital Episode Statistics), Death Registry and Primary Care (GP) providers. Some of the hospital diagnosis data is coded using ICD 10 codes, but some older data is coded using ICD 9 codes.   

UKB does not receive Snomed detailed ICD 10 - CM codes. These codes are used in the USA but not in the UK. Other linked health data is coded using Read V2 or CTV3, OPCS3, OPCS4, DM+D, or BNF. Data self-reported by participants is coded using custom UKB codings. These are specified in the Showcase page for each field.   

For more detail on the codings and linkages, see Showcase Resources: 596, 591, 592, 593, 126048, 115558, 115559, 2112, 141140, 138483, 146641, and the Description for Category 2000.