Evaluation of Prognosis

Evaluation of Prognosis

Glossary

·        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 disorder

·        Prognostic factor: 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 conditions present)

·        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

Using an article about prognosis

·        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 intervals

·        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?