Prognosis (Greek πρόγνωση - literally fore-knowing, foreseeing) is a medical term to describe the likely outcome of an illness.
When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because previous research found that this proportion of patients died. However, it is much harder to translate this into a prognosis for an individual patient: additional information is needed to determine whether a patient belongs to the 45% who will succumb, or to the 55% who survive.[1]
A complete prognosis includes expected time, function, and a description of the disease course such as progressive decline, intermittent crisis, or sudden, unpredictable crisis.
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Prognostic scoring is also used for other cancer outcome predictions. A Manchester score is an indicator of prognosis in small cell lung cancer. In Non-Hodgkin lymphoma, physicians have developed the International Prognostic Index to predict patient outcome.
Other medical areas where prognostic indicators are used is in Drug-Induced Liver Injury (DILI) (Hy's law) and use of an exercise stress test as a prognostic indicator after myocardial infarction.
Medical studies have demonstrated that most doctors are overly optimistic when giving prognostic information, that is, they tend to overstate how long the patient might live. For patients who are critically ill, particularly those in an intensive care unit, there are numerical prognostic scoring systems that are more accurate. The most famous of these is the APACHE II scale. However, this scale is most accurate in the seven days prior to a patient's predicted death.
Knowing the prognosis helps determine whether it makes more sense to attempt certain treatments or to withhold them, and thus plays an important role in end-of-life decisions.
Estimators that are commonly used to describe prognoses include:
For the 19th century physicians, particularly the French school, the main aim of medicine was not to cure disease, but rather to give a medical diagnosis and achieve a satisfying prognosis of the patient's chances. Only several decades later did the focus of efforts in Western medicine shift to curing disease.