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A timeframe (referred to as a reference period), fixed points in time (referred to as reference time points), 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 reference periods.
  • Dates, and times as applicable, for reference time points and/or milestones used as references.


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 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 reference time point 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 reference time point or milestone.


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

  • First, define the study reference period, reference 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 reference time point, 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 continued, in relation to the study reference period, reference time point, or milestone.


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


The following table describes the figures above.

NumFigure(s)ReferenceDescription
1Figure 1Study Reference Period
  • The study reference period is defined as the timeframe between a subject's first and last exposure to a tobacco product. This study reference period is part of the overall context of the study represented by B and C. 
  • 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.
    • 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.
    • 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 RFENDDTC represent the dates of the subject's first and last exposure dates respectively 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 3Fixed Point in Time
  • Two fixed points in time are defined for the subject, the subject's Screening visit and date of last contact. The fixed points in time are part of the overall context of the study represented by B and C. 
  • Observations about concomitant medications used by the subject with the timing of use are collected in relation to the fixed points in time; 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.
    • 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.
    • 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 Concomitant Medications (CM) dataset.  
      • CMSTRTPT and CMENRTPT represent values from collection variables CMPRIOR and CMONGO in the Concomitant Medications (CM) dataset.

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