1. identifying information (such as name or social security number) that would enable the investigator to readily ascertain the identity of the individual to whom the private information or specimens pertain has been replaced with a number, letter, symbol, or combination thereof (i.e., the code); and 2. a key to decipher the code exists, enabling linkage of the identifying information to the private information or specimens.
Source(s):
NISTIR 8053 from OHRP-Guidance on Research Involving Private Information or Biological Specimens