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CRITICAL ANALYSIS

PROGNOSIS



The three main questions to ask yourself about any report before applying its findings to your patients are:

1) Are the results valid?
2) What are the results?
3) Will the patients help me with my individual patient?

The data required to answer these questions varies between the domains and, depending upon the type of question, the types of evidence used.

Are the results valid?

BIAS: Because studies of prognosis tend to be either cohort studies or case-control studies, bias is of greater concern.  It is vital that the researchers describe clearly the inclusion and exclusion criteria for patients in the study.  

PATIENTS: It is important that all patients began the study at the same stage of disease.  This is easier to do in some cases than others and allowances may have to be made (but not ignored).  

BLINDEDNESS:  Investigators should be blinded to the presence of the existence of the prognostic factor when studying the results at the time of the outcome.  For example, they should be accounting for whether all patients were dead or alive, without knowledge of whether the prognostic factor was present.

FOLLOW-UP:  Particularly for a cohort study, follow-up must be sufficiently long to study the full progress of a condition.  Stopping a study on pregnancy at the sixth month, for example, is of little value.  It is vital that researchers account for all patients.  


What are the results?

Researchers are most likely to report survival curves, risk ratios, or odds ratios.  These are discussed in greater detail in the Important Concepts section on prognosis.   You will also want to know how precise the results are using confidence intervals .


Will the results help me in patient care?

Refer to the concerns discussed earlier .


The University of Alberta provides a worksheet for analyzing articles on prognosis.


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