Quest Diagnostics is testing its ability to be the world's leading clinical lab. The company performs diagnostics on some 157 million specimens each year, including routine clinical tests such as cholesterol checks, Pap smears, and HIV screenings. Quest Diagnostics also performs esoteric testing (such as genetic screening) and anatomic pathology testing (such as tissue biopsies for cancer testing). In all, the company serves half of the physicians and hospitals in the US as well as government agencies and other clinical labs. Quest Diagnostics has more than 2,300 patient service centers where samples are collected, and the Quest Diagnostic Nichols Institute where new diagnostics are developed.