Medical history

The medical history or anamnesis of a patient is information gained by a physician or other healthcare professional by asking specific questions, either of the patient or of other people who know the person and can give suitable information (in this case, it is sometimes called heteroanamnesis), with the aim of obtaining information useful in formulating a diagnosis and providing medical care to the patient. This kind of information is called the symptoms, in contrast with clinical signs, which are ascertained by direct examination. Most health encounters will result in some form of history being taken. Medical histories vary in their depth and focus. For example an ambulance paramedic would typically limit their history to important details such as name, history of presenting complaint, allergies etc. In contrast, a psychiatric history is frequently lengthy and in depth as many details about the patients life are relevant to formulating a management plan for a psychiatric illness.

The information obtained in this way, together with clinical examination, enables the physician to form a diagnosis and treatment plan. If a diagnosis cannot be made then a provisional diagnosis may be formulated, and other possibilities (the differential diagnosis) may be added, by convention listed in order of likelihood. The treatment plan may then include further investigations to try and clarify the diagnosis.

Process
A physician typically asks questions to obtain the following information about the patient:


 * Identification and demographics: The name, age, height, weight.
 * The "chief complaint (CC)" &mdash; the major health problem or concern, and its time course.
 * History of present illless (HOPI) - details about the complaints enumerated in the CC.
 * History of past illness (HPI)(including major illnesses, any previous surgery/operations, any current ongoing illness, eg diabetes)
 * Review of systems(ROS) Systematic questioning about different organ systems
 * Family diseases
 * Childhood diseases
 * Social history- including living arrangements, occupation, drug use (including tobacco, alcohol, other recreational drug use), recent foreign travel and exposure to environmental pathogens through recreational activities or pets.
 * Regular medications (including those prescribed by doctors, and others obtained over the counter or alternative medicine)
 * Allergies
 * Sex life, obstetric/gynecological history and so on as appropriate.

History-taking may be comprehensive history taking (a fixed and extensive set of questions are asked, as practised only by medical students) or iterative hypothesis testing (questions are limited and adapted to rule in or out likely diagnoses based on information already obtained, as practised by busy clinicians). Computerised history-taking could be an integral part of clinical decision support systems.

Review of systems
Whatever system a specific condition may seem restricted to, it may be reasonable to review all the other systems in a comprehensive history. A review of system (ROS) should cover these 14 subheadings according to the legal billing policies in the US:
 * Constitutional symptoms (e.g., fever, weight loss)
 * Eyes
 * Ears, nose, mouth, and throat
 * Cardiovascular
 * Respiratory
 * Gastrointestinal
 * Genitourinary
 * Musculoskeletal
 * Integumentary
 * Neurological
 * Psychiatric
 * Endocrine
 * Hematologic/lymphatic
 * Allergic/immunologic