myCSG © |Area: ADaM| Concept: C1009 : ADaM BDS - Analysis Flags | Lesson: L102 : Creation of ANL01FL, multiple record within an analysis visit. Closest and latest record will be chosen |

Some examples of record selection algorithms:

  • Select the earliest record within an analysis visit
  • Select the latest record within an analysis visit
  • Select the record that is closest to the target day within an analysis visit
  • Select the record with lowest/highest/worst result across postbaseline records
  • Select the records of the subject's who has experienced at least one 'Grade 4' lab toxicity

Background for an example analysis flag
  • In the analysis of clinical trial data, we often summarize data at each analysis visit as shown in the screenshot below

  • 'n' in the above table represents the number of subjects with non-missing result at that visit
  • Sometimes, there will be multiple records for the same subject and parameter at that analysis visit in the analysis data
  • For these tables, we need to use only one of those multiple records for analysis
  • We need a way to clearly identify which record will be used for analysis in these tables as the existing standard variables like USUBJID, PARAMCD, AVISIT are not sufficient to identify the record (as there are multiple records with same value in these variables)
  • One approach is to create an additional variable and populate it with a meaningful value to indicate that a specific record is used for analysis
  • The algorithm on which of those multiple records should be prespecified in the statistical analysis plan
  • Some common algorithms are:
    • Use the earliest record within the visit
    • Use the latest record within the visit
    • Use the closest record to the target day within the visit
    • Use the average result of all available records within the visit (by creating a new record) etc.

 

ADaM implementation
  • CDISC ADaM standard allows us to handle such scenarios using a set of variables called 'analysis flags' (ANLzzFL)
  • The lower-case letters "zz" in the variable name (ANLzzFL) is an index for the zzth variable where "zz" is replaced with a zero-padded 2-digit integer [01-99].
  • These analysis flags should only be used when the other existing standard variables are not sufficient to filter the records for analysis
  • In the above case, as the existing standard variables are not sufficient, we can create an analysis flag named ANL01FL and populate it with Y on the records used for analysis
VARIABLE_NAMEVARIABLE_LABELDERIVATION
AWTDIFF Analysis Window Diff From Target Set to the absolute difference between ADY and AWTARGET (that is, ABS(ADY-AWTARGET))
ANL01FL Analysis Flag 01 Set to "Y" on the record which is closest to target day with in an analysis visit.
If there exists multiple records which are closest, pick the latest record.
Complete SAS code to generate the output is available for registered users!

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