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A Universally Unique Identifier (UUID) is a randomly-generated, 32-digit hexadecimal value. 

UUIDs have replaced TCGA barcodes as the primary identifier of TCGA data for the following reasons:

  • TCGA has become more complex and the barcode structure cannot hold the data required (for example, shipping of portions, or sub-portioning of samples).
  • There are not enough barcode permutations to capture all the representations required.
  • Barcodes are coupled with the metadata that forms them, which becomes an issue when the metadata changes (for example, normal sample may be a tumor sample).

Because of these factors, TCGA has transitioned to a content-free ID for all biospecimens and clinical-related data. The DCC has chosen the Universally Unique Identifier (UUID) for this purpose, as it is a widely-accepted standard that has no limit (in practical terms) to the number of IDs possible.

As such, UUIDs are not meant for human consumption. That is, it is expected that only computers would come in contact with these identifiers while processing data. This eliminates human-introduced ID artifacts created through manual editing. The DCC will keep track of all UUIDs and provide all associated metadata.

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