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In general observation class domains, days relative to the reference start date or in relation to applicant-defined reference dates 

for observations

The SDTM allows for the representation of study days relative to the RFSTDTC reference start date variable in the DM dataset, using variables --DY, as described in Section 4.4.4, Use of the "Study Day" Variables. The calculation of additional study days within subdivisions of time in a clinical trial may be based on 1 or more sponsor-defined reference dates not represented by RFSTDTC. In such cases, the sponsor may define supplemental qualifier variables and the Define-XML document should reflect the reference dates used to calculate such study days. If the sponsor wishes to define "day within element" or "day within epoch", the reference date/time will be an element start date/time in the Subject Elements (SE) dataset (see Section 5.3, Subject Elements).

in general observation class domains?dates may be represented for observations.

Metadataspec
NumVariable PopulationImplementation

Days Relative to the Reference Start Date

Variables --DY, --STDY, and --ENDY represent days relative to the reference start date in RFSTDTC where the value of:

  • --DY is the relative day of the date populated in --DTC for the observation,
  • --STDTC is the relative day of the date populated in --STDTC for the observation; and
  • --ENDY is the relative day of the of the date populated in --ENDTC for the observation.

All relative day values will be integers and there will be no study day 0. The reference start date is considered day 1 and the study day value is increased by 1 for each date following the reference start date and decreased by 1 for each date prior to the reference start date, e.g.:

--DY = (date portion of --DTC) - (date portion of RFSTDTC) + 1 if --DTC is on or after RFSTDTC
--DY = (date portion of --DTC) - (date portion of RFSTDTC) if --DTC precedes RFSTDTC

Days Relative to Applicant-Defined Reference Dates

Applicants may represent days relative to applicant-defined reference dates. In such cases:

  • Values will be integers.
  • The reference date will be day 1.
  • Relative days will be represented in a nonstandard variable (NSV) in a --SUPP dataset associated with the domain. 






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