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This section addresses how to identify the records of an ADaM dataset that are used for analysis. The four specific issues addressed include: (1) identification of the records used in an LOCF analysis; (2) identification of the record containing the baseline value; (3) identification of post-baseline conceptual timepoint records, such as endpoint, minimum, maximum, or average; and (4) identification of specific records used in an analysis.

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Records Used in a Timepoint Imputation Analysis

  • This section considers the issue of how to identify records used in a timepoint-related imputation analysis as well as how to represent data imputed for missing timepoints in an ADaM dataset. LOCF (Last Observation Carried Forward) is one of the most commonly used timepoint-related imputation analyses and is therefore specifically mentioned. However, the methodology is general and is not restricted to LOCF analysis. WOCF (Worst Observation Carried Forward) analysis is also mentioned to emphasize the generalizability.
  • When an analysis timepoint is missing, the ADaM methodology is to create a new record in the ADaM dataset to represent the missing timepoint and identify these imputed records by populating the derivation type variable DTYPE.
  • For example, when an LOCF/WOCF analysis is being performed, create LOCF/WOCF records when the LOCF/WOCF analysis timepoints are missing, and identify these imputed records by populating the derivation type variable DTYPE with values LOCF or WOCF. All of the original records would have null values in DTYPE. It would be very simple to select the appropriate records for analysis by selecting DTYPE = null for Data as Observed (DAO) analysis, DTYPE = null or LOCF for LOCF analysis, and DTYPE = null or WOCF for WOCF analysis. This approach would require understanding and communicating that if the DTYPE flag were not referenced correctly, the analysis would default to using all records, including the DAO records, plus the records derived by LOCF and WOCF. To perform a correct DAO analysis, one would need to explicitly select DTYPE = null.






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