In general observation class domains, the dates and times (when appliable) observations were collected are represented in variable --DTC. In interventions and events class domains, variable --STDTC is used to represent the start dates and times (when applicable) of interventions and events. Variable --ENDTC is used in all general observation class domains to represent the end date and time (when applicable) of the observation.
The variables used to describe time can vary between point-in-time observations (e.g., body weights) and duration-based observations (e.g., food consumption).
When the date/time of collection is reported in any domain, the date/time should go into the --DTC field (e.g., EGDTC for Date/Time of ECG). For any domain based on the Findings general observation class (e.g., lab tests based on a specimen), the collection date is likely to be tied to when the source of the finding was captured, not necessarily when the data were recorded. In order to ensure that the critical timing information is always represented in the same variable, the --DTC variable is used to represent the time of specimen collection. For example, in the Laboratory Test Results (LB) domain, the LBDTC variable would be used for all single-point blood collections or spot urine collections. For timed lab collections (e.g., 24-hour urine collections) the LBDTC variable would be used for the start date/time of the collection and LBENDTC for the end date/time of the collection. This approach allows the single-point and interval collections to use the same date/time variables consistently across all datasets for the Findings general observation class. The following table illustrates the proper use of these variables. Note that --STDTC should not be used in the Findings general observation class and is therefore blank in this table.
Collection Type | --DTC | --STDTC | --ENDTC |
|---|---|---|---|
| Single-point Collection | X | ||
| Interval Collection | X | X |
Most domains, especially Findings domains, have basic timing variables expressing the actual timing of the observation. The variables used to describe time can vary between point-in-time observations (e.g., body weights) and duration-based observations (e.g., food consumption).
Actual timing for point-in-time observations is expressed through the following variables:
- --DTC is the date when the observation occurred. Depending on the precision of the date, this can represent just the date (e.g., 2010-12-31) or a date and time (e.g., 2010-12-31T08:00). The --DTC variable is expected for many Findings domains.
- --DY is the study day when the observation actually occurred, relative to the sponsor-defined RFSTDTC variable in the Demographics (DM) domain.
These variables are shown in Figure 4471A.
Some observations may be associated with an interval of time (e.g., a finding evaluated over 2 hours). The following variables enable the definition of these ranges:
- --ENDTC is the end date of the range of time when the observation occurred. Depending on the precision of the time, this can represent just the date (e.g., 2010-12-31) or a date and time (e.g., 2010-12-31T08:00).
- --ENDY is the end day of the range of time when the observation occurred, relative to the sponsor-defined RFSTDTC variable in the DM domain.
In these cases, the --DTC/--DY variables are used to define the start of the interval. These variables are shown in Figure 4471B, in a case where an observation spanned 2 days
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