prognosis
Meaning of prognosis: A statement about probability across many similar cases, which is why it can shift as new results and responses to treatment come in.
Definition of prognosis
Prognosis is the expected course of a disease or condition: how it is likely to progress, what complications or recurrence may follow, how much function is likely to be regained and, where relevant, the chance of survival. It is an estimate built from evidence about similar cases and from the particular features of one person's illness.
What goes into a prognosis?
| Factor | Why it counts |
|---|---|
| The diagnosis itself | Different diseases follow different courses regardless of anything else |
| Extent or stage | How far the disease has progressed at the point it is found |
| Grade or molecular features | How aggressively the disease is behaving at cell level |
| Response to treatment | Often the single most informative factor, and it is only known later |
| Other conditions and function | What else the person is living with, and how well they were before |
Because several of these are unknown at diagnosis, an early prognosis is the least certain one, and it is revised as results accumulate. Clinical practice guidelines often set out prognostic groupings so that similar cases are described consistently.
Why are survival statistics hard to read?
Figures such as five-year survival describe what happened to a large group of people diagnosed some years earlier and treated with what was then available. They say nothing about which individuals in that group did well. Median survival is the midpoint, meaning half the group lived longer, sometimes far longer, and a median is not a prediction for anyone. Relative survival compares a group with the general population rather than counting deaths from the disease alone. Statistics also lag: they describe past treatment, so they can understate what current treatment achieves. Where the underlying studies are graded, the levels of evidence indicate how much weight a prognostic claim can carry.
How does prognosis differ from diagnosis?
A diagnosis names what the condition is and rests on findings that can be checked. A prognosis states where it is likely to go and rests on probability, so it can be wrong in an individual case without having been unreasonable. A diagnosis usually stays fixed once confirmed; a prognosis is expected to change. It also covers more than survival, taking in the chance of recurrence, the likely level of function and independence, and the complications that may arise along the way, all of which may matter more to a particular person than length of life alone.
Also known as
Used in a sentence
The specialist discussed the likely prognosis and treatment options.
Good to know
A prognosis expresses probability rather than certainty, describes groups of similar cases rather than an individual, and changes as new information becomes available.
Word origin
Where “prognosis” comes from
From Greek pro-, meaning before, and gnosis, meaning knowledge.