What are the general guidelines to SDTM variables?
Each of the SDTM domains has a collection of variables associated with it. There are five roles that a variable can have: Identifier, Topic, Timing, Qualifier, and for trial design domains, Rule. Using lab data as an example, the subject ID, domain ID and sequence (e.g. visit) are identifiers. The name of the lab parameter is the topic, the date and time of sample collection are timing variables, the result is a result qualifier and the variable containing the units is a variable qualifier. Variables that are common across domains include the basic identifiers study ID (STUDYID), a two-character domain ID (DOMAIN) and unique subject ID (USUBJID). In studies with multiple sites that are allowed to assign their own subject identifiers, the site ID and the subject ID must be combined to form USUBJID. Prefixing a standard variable name fragment with the two-character domain ID generally forms all other variable names. The SDTM specifications do not require all of the variables associated w
