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The reference specifications introduces the Reference Dataset Structure. A Reference Dataset Structure dataset contains one record per combination of Stratum values. At least one stratum variable is required and up to 99 stratum variables can be present in a reference dataset. There may several reference datasets in a study. This section of the TIG defines the standard variables used in reference datasets.

Reference dataset names must have a prefix of RF. There are then up to 6 characters that should be used to make dataset name meaningful. However, In the ADaM standard there are currently no predefined dataset names besides for ADSL.

• Proposed names for the datasets in the example section are:
  • RFBR (Reference Data for Birthrate)
  • RFIP (Reference Data for Initial Population)
  • RFMIGRAT (Reference Data for Migration Rates)
  • RFMORT (Reference Data for Mortality Rates)
  • RFTRANSP (Reference Data for Transition Prob)

One of the use cases of a reference dataset is to capture historical data based on previous studies data. The individual historical data concept is described in the INPRM (Input Parameter) variable and the value of the INPRM (Input Parameter) concept is captured in the INPRMVAL (Input Parameter Value) variable. These values may change over time depending on the reference data and therefore is only a snapshot of data at a point in time.  <??? Should we have a variable to identify the source (date/time/etc) since it may change over time ??? or is this not necessary or left for the dataset metadata??> There is also a variable INPRMU (Input Parameter Unit) which can be used to capture the unit associated with the parameter value is applicable. Some examples of units are ratios and counts. See the Population Health ADaM examples section for some examples of reference datasets.

The identifier variables associated with the reference values are captured in the STRTMy (Stratum y) variables. The actual values of the STRTMy variables are captured in the  STRVALy (Stratum y Value) variables As many identifiers as necessary based on the source data should be captured in the reference dataset and the order of the stratum variables has no inherent meaning so ordering is not defined in this section. The convention of y is used as an index value indicating an integer with a value of 1-99 (as described in the ADaM standard section). There is no requirement that the stratum variables start with 1, nor must the variables use consecutive values. Some examples of stratum variables are Year, Sex, Race, Age, Transition type, and product.

Proposed standard structure designed to capture reference data that is not captured in SDTM and may be used as input into SDTM or ADaM creation