Users' Guide:Prognosis
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Are the results valid?
What are the results?
Will the results help me in patient care?
Understanding an Article on Prognosis

Are the results valid?

Was there a representative and well-defined sample of patients at a similar point in the course of disease?

• Inclusion and exclusion criteria?
• Selection biases?
• Stage of disease?

Was follow-up sufficiently long and complete?

• Reasons for incomplete follow-up?
• Prognostic factors similar for patients lost- and not lost-to-follow-up?

Were objective and unbiased outcome criteria used?

• Outcomes defined at start of study?
• Investigators 'blind' to prognostic factors?

Was there adjustment for important prognostic factors?

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What are the results?

How likely are the outcomes over time?

• Survival curves?

How precise are the estimates of likelihood?

• Confidence intervals?

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Will the results help me in patient care?

Were the study patients similar to my own?

• Patients similar for demographics, severity, co-morbidity, and other prognostic factors?
• Compelling reason why the results should not be applied?

Will the results lead directly to selecting therapy?

Are the results useful for reassuring patients?

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Understanding an Article on Prognosis

The prognosis of a disease refers to its possible outcomes and the likelihood that each one will occur.

A prognostic factor is a patient characteristic that can predict that patient's eventual outcome:

• demographic: e.g. age
• disease-specific: e.g. tumor stage
• comorbid: other conditions present

Prognostic results are the number of events that occur over time, expressed in:

• absolute terms: e.g. 5 year survival rate
• relative terms: e.g. risk from prognostic factor
• survival curves: cumulative events over time

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