Relative timing variables are sets of variables that provide information about how the timing of the record relates to either the study reference period or another fixed point in time. CDASH relative timing variables are collected for observations where a date either is not collected or is not available. The CDASH set of variables serve as an indicator (or flag) that the observation's "start" was prior to the study reference period or prior to another fixed point in time OR that the observation's "end" was after or ongoing as of the study reference period or another fixed point in time. The CDASH variables of --PRIOR and --ONGO serve this purpose. How these CDASH flags are translated to SDTM (according to controlled terminology) depends on whether the comparison is against the protocol-defined study reference period or against another fixed point in time serving as the "reference" for the timing of the record. To emphasize, collection of these CDASH relative timing variables is always dependent on the actual date either being prospectively not collected or not available. For more information, see Section 8.1.1, General CDASH Assumptions for Interventions Domains, and Section 8.2.1, General CDASH Assumptions for Events Domains.
For all SDTM submissions, there is a defined timeframe (the study reference period). According to SDTMIG, the start and end dates of the study reference period are submitted in the variables RFSTDTC and RFENDTC. The defined period may be protocol-specific or set by company policy, standard operating procedures, or other documented procedures. The study reference period might be defined as being from the date/time of informed consent through the date/time of subject's completion of the study, or it might be from the date/time of first dose to the date/time of last dose. Regardless of how the study reference period is defined, the dates (and optionally times) of the start and end of that period must be collected.
If there is a need to collect information about whether an observation of interest occurred prior to a reference point or milestone other than the beginning of the study reference period, or was ongoing or continuing at some reference point or milestone in the study other than the end of the defined study reference period, the date/time of that reference point or milestone should also be collected. If this date/time has been collected, reasonable comparisons can be made to that date/time with “prior”, “coincident”, “continuing”, or “ongoing” questions.
The following steps should be taken to ensure observations of interest that occur over time can be related to the study reference period or to a fixed point in time/milestone in a meaningful way. Figure 1 provides a representation of an intervention as it relates to the study reference period, and Figures 2 and 3 provide a representation of comparisons related to other fixed points in time or a milestone.
Study Reference Period
Define the “on-study” period (B-C). Once the overall on-study period has been defined (B-C), collect the dates/times of the start of the study reference period (e.g., date of informed consent, date of first dose) and end of the study reference period (e.g., date of last contact, date of last dose), as part of the clinical data with their respective domains (e.g., Disposition (DS), Exposure (EX)). These dates will map into the RFSTDTC (B; start of Study Reference Period) and RFENDTC (C; end of Study Reference Period) variables in the SDTMIG Demographics (DM) dataset.
- Collected comparisons (D, E) use CDASHIG variables (e.g., “prior”, “ongoing”) for when something started or ended, in relation to the on-study reference period (i.e., RFSTDTC-RFENDTC: B-C). These CDASH variables are used to populate the SDTMIG variables--STRF and --ENRF variables when the SDTM-based datasets are created.
Note: These relative timing variables are only populated in the SDTM -based datasets when a date is not collected.
Fixed Point in Time/Milestone
- Define the fixed point in time or milestone (B or C). The fixed point in time or milestone can be a date or a description. This will map into the SDTMIG variables --STTPT or --ENTPT when the SDTM-based datasets are created.
- Collected comparisons (D or E) use CDASHIG variables (e.g., “prior”, “ongoing”) for when something started or ended, in relation to the fixed point in time or milestone (B or C). These CDASH variables are used to populate the SDTMIG variables--STRTPT or --ENRTPT when the SDTM-based datasets are created.
Note: These relative timing variables are only populated in the SDTM-based datasets when a date is not collected.
For information about mapping what is collected in “prior”, “ongoing”, and “continuing” fields into the appropriate SDTMIG variables, see SDTMIG
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