Answer
1. Chest X-ray and blood tests are not usually required for children under the age of fifteen.
2. Applicants with mental retardation or learning disabilities must present a report of their condition and any special educational or supervision requirements.
3. Medical eligibility is a requirement of INA Sections 212(a) and 221(d). Failure to provide required information may cause delay or denial of immigrant visas. If an immigrant visa is not issued, all medical eligibility forms will be treated as confidential under INA Section 222(f).
4. The applicant must show his/her passport (or other photo identification) and appointment letter to the doctor during the medical examination.
The medical examination will include a medical history review, physical examination, chest X-ray and blood tests for syphilis.
The physical examination will at least include examination of the eyes, ears, nose and throat, extremities, heart, lungs, abdomen, lymph nodes, skin and external genitalia.
In some countries, the panel physician will send the results to the U.S. Embassy/Consulate directly. In other countries, the panel physician will give the applicant his/her medical exam results in a sealed envelope and an x-ray which the applicant must bring to the interview.
Note: The medical examination is not a complete physical examination. Its purpose is to screen for certain medical conditions relevant to U.S. immigration law. The panel physician is not required to examine you for any conditions except those the U.S. Public Health Service specifies for U.S. immigration purposes, nor is the physician required to provide you with diagnosis or treatment even though other matters related to your health might be discovered. This examination is not a substitute for a full physical examination, consultation, diagnosis, or treatment by your primary health care provider.
For more FAQ's on Medical Examination please visit this link
http://travel.state.gov/visa/immigrants/info/info_3745.html#page