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The optional grouping identifier variable --GRPID may be used in all domains based on the general observation classes. --GRPID identifies relationships between records within a USUBJID within a single domain and has no inherent meaning across subjects or across domains. Relationships between observations are defined by assigning the same unique character value to the --GRPID variable for sets of related observations. The values used for --GRPID can be any values the applicant chooses; however, if the applicant uses values with some embedded meaning (rather than arbitrary numbers), those values will be consistent.  

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