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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
Questions to Ask Yourself
Are the results valid?
1. 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?
2. Was follow-up sufficiently long and complete?
Reasons for incomplete follow-up?
Prognostic factors similar for patients lost- and not lost-to-follow-up?
3. Were objective and unbiased outcome criteria used?
Outcomes defined at start of study?
Investigators 'blind' to prognostic factors?
4. Was there adjustment for important prognostic factors?
What are the results?
1. How likely are the outcomes over time?
Survival curves (Kaplan-Meier)?
2. How precise are the estimates of likelihood?
3. Did the study have a sufficiently large sample size?
Vanderbilt- Power and Sample Size Calculator
Will the results help me in patient care?
1. 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?
2.Will the results lead directly to selecting therapy?
3. Are the results useful for reassuring patients?