Source:http://linkedlifedata.com/resource/umls/id/C2347789
NCI: Relatively uniform groups (e.g. etiologically and pathogenetically more homogeneous, racial, ethnic, or gender-specific, or the disease- or condition-specific) of study subjects formed within a clinical study population for a separate analysis. The selection of the subgroups, methods of subgroup analysis , and anticipated difference in observation outcome(s) have to be defined and justified in the study protocol and based on known biological mechanisms, and/or findings in previous studies.