There are several different types of appointment letters a claimant may receive from Social Security in response to an application for benefits. One letter may contain a notice that a medical examination has been schedules by the Disability Determination Services which is a State agency that evaluates all disability claims for the Social Security. A second commonly received letter is a notice sent by the Office of Hearings and Appeals indicating that a hearing date has been set. It is important for claimants to acknowledge receipt of appointment letters and to follow that instructions or requests they notice or adverse actions may result.