Reference Dates and Relative Timing

A timeframe (referred to as a study reference period), 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 are related. The following will be collected using TIG Collection or CDASH Model Timing fields when references for the timing of other observations are defined:

• Start and end dates, and times as applicable, for study reference periods.
• Dates, and times as applicable, for fixed points in time and/or milestones used as references.

The date, and time as applicable, of an observation timing related to a reference will be collected whenever possible. Only in cases where it is not possible to collect the date of a related observation (e.g., the date is not available), will a relative timing for the observation in relation to a reference be collected. Relative timing will be collected using TIG Collection Variables:

• --PRIOR to indicate the timing of the observation was prior to the start date of a study reference period or the date of a fixed point in time or milestone; or
• --ONGO to indicate the timing of the observation was ongoing relative to the end date of a study reference period or the date of a fixed point in time or milestone.

The following steps should be taken when designing CRFs to ensure observations of interest can be related to study reference periods, fixed points in time, and/or milestones. 

• First, define the study reference period, fixed time point, or milestone in the context of the study. 
• Collect the start and end date/times of the study reference period, the date/time of the fixed timepoint, or date/time of the milestone using appropriate TIG Collection or CDASH Model fields. 
• Collect relative timing as needed using fields --PRIOR and --ONGO (e.g., “prior”, “ongoing”) for when an observation started or ended, in relation to the study reference period, fixed time point, or milestone.

The figures below show collection of relative timing in relation to a study reference period and a fixed time point. Relative timing in relation to a milestone is collected in the same way as for a fixed timepoint. Representation of collected reference dates and relative timing in tabulation datasets is indicated below and further described in Section x.x, Assumptions for Observation Classes and Section x.x Add tabulation section link.

Figure.Standards for Collection Reference Dates and Relative Timing