Evaluation of Prognosis
Prognosis: the possible outcomes
of a disease or condition and the likelihood that each one will occur.
How to estimate your patient‟s
likely clinical course over time, or anticipate likely complications of the
characteristics associated strongly enough with a condition‟s outcome to
predict accurately the development of these outcomes. E.g. demographic (e.g.
age), disease specific (e.g. tumour stage), or co-morbidity (e.g. other
Prognostic results are the number
of events occurring over time, expressed in absolute terms (e.g. 5 year
survival rate), relative terms, or survival curves
Risk factor: patient
characteristics associated with an increased probability of developing a
disease in the first place. Neither prognostic or risk factors imply a cause
and effect relationship
· Are the results of the study valid?
o Was there a representative and well-defined sample of patients at a similar point in the course of the disease? (ideally at its onset). Is the disease clearly defined (what are the inclusion/exclusion criteria)? Is the sample representative of the whole spectrum of disease? Sources of bias: e.g. selection bias (referrer bias) or lead-time bias
o Was follow-up sufficiently long and complete (what were the potential
characteristics of those lost to follow-up?
o Were objective and unbiased outcome criteria used? Were the investigators blind?
o Was there adjustment for important prognostic factors? Were subgroups
with different prognoses stratified?
What are the results?
o How large is the likelihood of the outcome event(s) in a specified
period of time
o How precise are the estimates of likelihood? Precision best expressed in confidence
Will the results help me in
caring for my patients?
o Were study patients similar to my own?
o Will the results lead directly to selecting or avoiding therapy?
o Are the results useful for reassuring or counselling patients?