Table 1 Mapping rules after sequences A, B and C

To give priority to concepts from the 'disorder' or 'finding' hierarchy in SNOMED CT over 'morphological structure', 'body structure' or 'context depending category'/'situation concepts'

Choosing 'malignant lymphoma (disorder)' instead of 'malignant lymphoma (morphologic abnormality)

Not to use 'navigational' concepts

'Navigational concepts' is a child to the top-level concept 'Special concept'. These concepts are not part of active clinical terminology.

To thoroughly analyse if the Z-categories in chapter XXI of ICD-10 refer to procedures or states

Chapter XXI refers to 'factors' and 'circumstances other than a disease, injury or external cause' but does not state that many of the categories in the chapter seem to be referring to procedures; for example, 'Z 32-P Pregnancy examination'. Our decision was to map categories referring to procedures to procedure-concepts in SNOMED CT.

To consider the 'exclude' rule in ICD-10 as a rule that does not exist in SNOMED

The classification rule that 'excludes' categories both on a category and a chapter level is not present in SNOMED CT

To adhere to strict rules of priority regarding master data information sources for the classification categories in KSH97-P

There were several sources regarding master data in both English and Swedish that had to be ranked, since the sources were sometimes in conflict.

To give priority to order of terms in the original master category text in cases where the concepts were partly matched to SNOMED CT

'Other disorders of kidney and ureter' where 'disorder of kidney' should be chosen if the whole category could not be covered in a SNOMED CT concept.