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 are 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 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 reference periods
  • Dates, and times as applicable, for reference time points

The date, and time as applicable, of an observation to be 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 collection variables:

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

The following steps should be taken when designing CRFs to ensure observations of interest can be related to reference periods and reference time points. 

  1. Define the reference period and/or reference time point(s) in the context of the study. 
  2. Collect the start and end date/times of the reference period and/or the date/time of the reference time point(s) using appropriate TIG collection or CDASH Model fields. 
  3. Collect the actual timing of observations when it is possible to collect the date(s) for a related observation.
  4. Collect relative timing of observations when collection of actual dates is not possible using fields --PRIOR and --ONGO (e.g., “prior”, “ongoing”) for when an observation started or continued, in relation to the study reference period and/or reference time point(s).

The figures below show examples of collection of relative timing in relation to a reference period and reference time points; the table that follows describes the figures. Representation of collected reference dates and relative timing in subsequent tabulation datasets is noted below and further described in Section 2.8.7.6, Representing References and Relative Timing.

NumFigure(s)ReferenceDescription
1Figure 1Reference period
  • The reference period is defined as the timeframe between the reference start date for the subject and the reference end date for the subject. This reference period is chosen by the applicant according to the needs of the study and may vary. In Figure 1 the study reference period corresponds to the time between subjects' first and last exposure to a tobacco product, which is a typical scenario for a study reference period. This reference period (represented by the time between B and C) is part of the overall context of the study. 
  • Observations about concomitant medications used by the subject with the timing of use are collected in relation to the study reference period:
    • For A, the start and end dates for the concomitant medication are known and are collected.
      • Collection fields CMSTDAT and CMENDAT are used to collect the start and end dates for the concomitant medication.
    • For D, the start date for the concomitant medication is unknown and cannot be collected.
      • Collection field CMPRIOR is used to collect that the known start of the concomitant medication relative to exposure is prior to the subject's first exposure. 
      • Collection field CMENDAT is used to collect the known end date.
    • For E, the subject has not discontinued the concomitant medication and therefore the end date for the concomitant medication cannot be collected. 
      • Collection field CMSTDAT is used to collect the known start date.
      • Collection field CMONGO is used to collect that the use of the concomitant medication is ongoing relative the subject's last exposure.
  • The following variables are used to represent collected data in subsequent tabulation datasets:
    • RFSTDTC and RFENDTC represent the dates of the subject's first and last exposure to the tobacco product (per Figure 1), respecticely, in the Demography (DM) dataset.  
    • CMSTRF and CMENRF represent values from collection variables CMPRIOR and CMONGO in the Concomitant Medications (CM) dataset.
2Figures 2 and 3Reference time point
  • Two reference time points are defined for the subject: the screening visit and the date of last contact. The reference time points (represented by B and C) are part of the overall context of the study. 
  • Observations about concomitant medications used by the subject with the timing of use are collected in relation to the reference time points:
    • For A, the start and end dates for the concomitant medication are known and are collected.
      • Collection fields CMSTDAT and CMENDAT are used to collect the start and end dates for the concomitant medication.
    • For D, the start date for the concomitant medication is unknown and cannot be collected.
      • Collection field CMPRIOR is used to collect that the known start of the concomitant medication relative to Screening is prior to the subject's screening visit. 
      • Collection field CMENDAT is used to collect the known end date.
    • For E, the discontinuation date for the concomitant medication is unknown and cannot be collected. 
      • Collection field CMSTDAT is used to collect the known start date.
      • Collection field CMONGO is used to collect that the use of the concomitant medication is ongoing relative the subject's date of last contact.
    • The following variables are used to represent collected data in subsequent tabulation datasets:
      • CMSTTPT and CMENTPT represent the date or a short description of the subject's screening visit and last contact respectively in the CM dataset.  
      • CMSTRTPT and CMENRTPT represent values from collection variables CMPRIOR and CMONGO in the CM dataset.

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