myCSG © |Area: ADaM| Concept: C1006 : ADaM BDS - Baseline Concepts | Lesson: L101a : Creation of baseline flag, base, chg and pchg variables |

Baseline result

  • In clinical trials, we often want to see how the treatment is affecting a particular test/parameter value
    • Example: How is the treatment impacting the systolic blood pressure value of a subject
  • For this, we need to have something as reference - a result which is collected prior to administering any treatment, to compare with post treatment values
  • The pre-treatment value is generally considered as 'baseline' result
  • The post-treatment results are then compared with baseline result and this comparison is generally the difference between post-treatment value and baseline result
  • This difference is called as 'change from baseline'
  • Sometimes, the percentage change from baseline at post-treatment timepoint is also needed

ADaM implementation

  • ADaM datasets support this baseline and change from baseline related analysis
  • ABLFL variable is used to indicate the baseline result
  • BASE variable is used to populate the baseline result of a parameter of that subject
  • CHG variable is used to populate the change from baseline result
  • PCHG variable is used to populate the percentage change from baseline result
VARIABLE_NAMEVARIABLE_LABELDERIVATION
ADT Analysis Date Extract the date portion from VSDTC and convert it to numeric value
PARAM Parameter Set to propcase(VSPOS)||VSTEST||" ("||VSSTRESU||")
PARAMCD Parameter Code If VSPOS="SITTING" and VSTESTCD="SYSBP" then set to "STSBP",
Else if VSPOS="SITTING" and VSTESTCD="DIABP" then set to "STDBP"
PARAMN Parameter (N) If PARAMCD="STSBP" then set to 1,
Else if PARAMCD="STDBP" then set to 2.
AVAL Analysis Value Set to VSSTRESN
AVISIT Analysis Visit A. For the souce records:
     If VS.VISIT="SCREEN 1" then set to "Screening 1",
     Else if VS.VISIT="SCREEN 2" then set to "Screening 2",
     Else set to propcase(VS.VISIT)
B. For the record with ABLFL="Y" set to "Baseline"
AVISITN Analysis Visit (N) A. For the souce records:
     If VS.VISIT="SCREEN 1" then set to -2,      Else If VS.VISIT="SCREEN 2" then set to -1,      Else Set to VS.VISITNUM
B. For the record with ABLFL="Y" set to 0
ABLFL Baseline Record Flag Set to "Y" on the latest record with non-missing result on or before treatment start date for each parameter within a subject
BASE Baseline Value Populate the AVAL from the record where ABLFL="Y" across all records of parmeter within a subject
CHG Change from Baseline Set to AVAL-BASE on the records where ADT>TRTSDT>.
PCHG Percent Change from Baseline Set to CHG/BASE*100 on records where ADT>TRTSDT>. and BASE is not in (0,.)
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