Predicting life expectancy is not easy and it is as much an art as a science. Being able to make a reasonable, educated guess about a patient's illness trajectory and the likely prognosis is important because:
Some patients(and their relatives) want to know prognosis
Knowing the prognosis helps inform decisions regarding how aggressively to treat complications as they arise
A key element to determining prognosis is to understand the natural history of the particular disease that the patient suffers from. The course and natural history of end-stage organ failure(e.g. liver failure due to cirrhosis) is very variable and is often quite different from that of advancing cancer. Similarly, dementia and degenerative neurological conditions typically have a different course towards the end of life than advancing cancer.
Objective Measures To Help With Prognosis
Numerous studies have confirmed that, in most circumstances, doctors tend to over-estimate life-expectancy and prognosis in patients with palliative illnesses. A number of clinicians have attempted to develop tools such as the Palliative Prognostic Index to help increase the accuracy of prognostication.
Performance State in an Advancing Terminal Illness
For patient's who are gradually declining, their performance score or functional status is often very helpful in helping inform assessments about prognosis. As a rule of thumb, patients who are declining quickly, tend to keep declining quickly, and those who are declining slowly tend to continue to decline slowly.
ECOG Performance Score
Probably the most widely used performance scale in oncology is the Eastern Co-operative Oncology Group(ECOG) scoring. This scoring system is often used in determining a patient's fitness for chemotherapy. When the ECOG score is 0 or 1 a patient would typically be considered fit for chemotherapy, where if the score is 2, 3 or 4 the patient may not be considered fit for chemotherapy.
ECOG Score
Features
0
Fully active with no performance restrictions
1
Strenuous physical activity is restricted but fully ambulatory and able to carry out light work
2
Capable of all self-care but unable to carry out any work activities; up and about > 50% of waking hours
3
Capable of only limited self-care; confined to bed or chair > 50% of waking hours
4
Completely disabled and totally confined to bed or chair
Karnofsky Performance Score
The Karnofsky Score is similar to the ECOG scoring system but is more detailed and more palliative care focussed. The Australian-modified version of it is widely used as it specifically designed for use in both a community and inpatient setting.
AKPS
Features
100
Normal with no evidence of disease
90
Able to carry out normal activity with only minor symptoms of disease
80
With some effort able to carry out normal activity with some symptoms of disease
70
Cares for self but unable to carry on normal activity or to do active work
60
Mostly able to care for mostly but requires occasional assistance
50
Considerable assistance and frequent medical care required
40
In bed more than 50% of the time
30
Almost completely bedbound
20
Totally bedboundand requiring extensive nursing care by professionals or family
10
Comatose or barely rousable
0
Dead
Specific Prognosis Scoring Tools
There are a number of prognostic scoring tools that are relatively well known in the palliative care world, including:
Objective Measures To Help With Prognosis