The grade, which is assigned to about 3,000 general acute-care hospitals across the nation twice a year, is based on how hospitals and other health care organizations protect their patients from errors, injuries, accidents and infections. The score comes from hospitals’ performance on more than 30 national measures from the Centers for Medicare and Medicaid Services (CMS), the Leapfrog Hospital Survey and other data. The state’s largest hospital and only academic medical center scored a C for the fourth year in a row. No Mississippi hospitals received an F grade, and one hospital received a D: Merit Health Biloxi. Each grade is based on hospitals’ performance in five categories: infections, problems with surgery, safety problems, practices to prevent errors, and doctors, nurses and hospital staff.