Representing References and Relative Timing

Timeframes, fixed points in time, and other milestones may be defined in the context of a study as references to which the timing of other collected observations is related. In such cases, timeframes are referred to as reference periods and such fixed points in time and milestones are referred to as reference time points.

The start and end dates (and times when applicable) of a reference period in a study are represented using variables RFSTDTC and RFENDTC respectively in the Demograph

In general observation class domains, days relative to the reference start date or in relation to applicant-defined reference dates may be represented for observations.

Num

Variable Population

Implementation

1

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

2

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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Representing References and Relative Timing