Requesting study definition variables

To request new functions that create variables via a study definition, follow these instructions:

  • Browse the study definition variables page to see all possible variables that can currently be extracted with a study definition, and check that the variable you want doesn't already exist. If you're not sure, read about OpenSAFELY study definitions to understand the way in which the database is queried and data extracts are generated.
  • Browse the data sources page to see what data is available in each backend.
  • View the OpenSAFELY-TPP database update notebook to see when each data source was updated.
  • View the OpenSAFELY-TPP schema notebook to see the structure of the database.
  • Check that the variable has not already been requested as an Issue in the cohort-extractor repository. Look at both open and closed Issues in case the variable has been considered by deemed unworkable or low priorty.

If after reviewing these resources you think the information you need might be in the database, but you can’t extract it with a study definition (for example because the variable extractor function doesn’t exist, or the structure of extracted data doesn’t allow for it), then:

  • Create a new Issue in the cohort-extractor repository, and add the enhancement label
  • Explain the rationale
  • Where possible, describe how you expect the function to look for this variable, or how it will modify or enhance an existing variable:
    • what will it be called?
    • what are the function arguments?
    • what are the returning values?
  • Where possible, provide example SQL code for the underlying database query (it doesn't have to be perfect).