ICD9 Mapping Question
Fri, 08/13/2010 - 13:49 — doug.meil
Hi there-
We noticed that, for example, the following ICD9 codes don't appear to have any SNOMED map in the SOURCE_TO_CONCEPT_MAP file, specifically where the target_vocabulary_code is = '01' (i.e., SNOMED). We see the target codes map to themselves (e.g., target and source are '02'). Are we interpreting this correctly?
250.01
250.0
250.10
250.12
250.13
250.22
250.23
250.30
250.31
250.33
250.40
250.42
250.43
250.50
250.52
250.53
250.60
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ICD9 Mapping response
Those ICD9 codes do map into SNOMED via the OMOP intermediate concepts. The reason is, those ICD9 source codes map to multiple SNOMED concepts, but in order to ensure a one-to-one mapping in the SOURCE_TO_CONCEPT_MAP table, there are surrogate concepts created (TARGET_VOCABULARY_CODE = 53) that allows you to map from ICD9 -> intermediate, and then in the CONCEPT_RELATIONSHIP from intermediate -> SNOMED. There are many instances of this, the Diabetes examples you’ve provided are just a handful. The general process to handle these cases is described in the Vocabulary specification document (link). In general, though, it is possible that some ICD9 codes don’t map to SNOMED…those would be the ICD9 source codes that don’t have corresponding records in SOURCE_TO_CONCEPT_MAP to either TARGET_VOCABULARY_CODE = 01 (SNOMED) or 53 (OMOP intermediate).
Thank you, OMOP Research Team