Down syndrome

This codelist was taken from OpenCodelists, created by OpenSAFELY. We recommend viewing this Phenotype on the OpenCodelist website to view the most recent version.

Diagnoses of Down syndrome

© University of Oxford for the Bennett Institute for Applied Data Science 2025. This work may be copied freely for non-commercial research and study.

Searched for "down", "trisomy", and "mongol" (as historical codes may use this term).

Removed unrelated codes (e.g. "falling down"), screening tests, family history codes, and suspected Down syndrome. Suspected Down syndrome was not included, as this codelist is aiming for a codelist for adults with high positive predictive value. Positive antenatal screening tests were not included, as these may be recorded in the mother's record rather than the child's. Discussed mosaicism with Hannah Kuper at LSHTM - agreed to include, since it is unlikely to be diagnosed and recorded if the individual has experienced no clinical consequences.

The codelist was restricted to diagnoses, therefore the following relevant codes were not included, since they were not considered sufficient standalone evidence of Down syndrome: • Down's facies(X7694) • Mongoloid tilt(X75ew) • Downs syndrome \& dementia checklist(Y2935) • Down's syndrome body mass index centile(Xabdn) • Down's syndrome height centile(Xabdt) • Down's syndrome weight centile(Xabdv)

Compared to the wider codelist in https://codelists.opensafely.org/codelist/opensafely/intellectual-disability-including-downs-syndrome/2020-08-27/ to check for any omissions, but Down syndrome codelist was consistent with this.

Included codes were kindly reviewed by Hannah Kuper.