Visit this site http://www.whatismedicalinsurancebilling.org/2010/06/bcbs-alpha-prefix-list-and-claim.html for more information on BCBS prefix list. The prefixes identify the member's BCBS prefix list plan or national account and become essential when routing claims for processing. In plan-specific alpha prefixes, the first two characters denote a given plan, while the third character identifies the product type chosen by the member, explains the BCBS of Texas. For instance, the" Z" and "G" in the prefix "ZGP" are BCBS-assigned letters, and the" P" denotes a preferred provider organization, or PPO, product. 

BCBS alpha prefix list