Hospitals keep contracts with HMOs and PPAs.
D003284:Contract Services / Q000639:trends; D003625:Data Collection; D006279:Health Maintenance Organizations / Q000458:organization & administration*; D006761:Hospitals; D007348:Insurance, Health / Q000458:organization & administration*; D011243:Preferred Provider Organizations / Q000458:organization & administration*; D013223:Statistics as Topic; D014481:United States