Valued at a market cap of $20.5 billion, Quest Diagnostics Incorporated (DGX) is a clinical laboratory company that provides diagnostic testing, information, and services to physicians, hospitals, employers, and health plans. The Secaucus, New Jersey-based company operates an extensive network of laboratories, patient service centers, and mobile phlebotomy services. Companies valued at$10 billion or more are typically classified as “large-cap stocks,” and DGX fits the label perfectly, with its market cap ...