Which organization is a not-for-profit private health insurance provider with membership ID numbers starting with three letters?

Blue Cross Blue Shield is the organization recognized as a not-for-profit private health insurance provider, which typically issues membership identification numbers beginning with three letters. This format of membership IDs is part of their standard operating procedures and helps in managing claims and member identification efficiently.

The other organizations listed, while also significant players in the health insurance sector, might not necessarily follow this specific ID format. For example, Aetna, Cigna, and Humana have different variations in their identification systems and may not always start with three letters. Understanding the specific characteristics of each company, such as their membership ID formats, can allow for more accurate identification and use of their services in coding and billing scenarios.