Days within a study may be represented In general observation class domains, days relative to the reference start date represented in variable RFSTDTC or in relation to applicant-defined reference dates.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?
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| Num | Variable Population | Implementation |
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| Study Days in Relation Relative to the Study Reference Date(--DY, --STDY, --ENDY)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 study day of the date populated in --DTC for the observation,
- --STDTC is the relative study day of the date populated in --STDTC for the observation; and
- --ENDY is the relative study day of the of the date populated in --ENDTC for the observation.
All study 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
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| Study Days Relative to Applicant-Defined Reference Dates | Applicants may represent days relative to applicant 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).: - 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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