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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?

If the study is a clinical trial, the measure of validity is the same as for therapy .

If the study is a cohort study, the measure of validity is the same as for prognosis .

If the study is a case-control study, then you will need to consider the following issues.

BIAS:   Case-control studies are susceptible to recall bias.  When you start to base your research on things that have happened in the past, you are assuming that the records actually represent the past.  For example, there is a brief period of time that you cannot count on patients who died of AIDS to have been written up that way.  Interviewer bias occurs when the study personnel prod survivors or clinicians for the data they're looking for by the nature of their questions.

PATIENTS:  Except for the exposure under study, were the compared groups similar to each other.  Were other known risk factors adjusted for?

RELATIONSHIP:  In order to show that an exposure results in a particular outcome, two things must be true.  The exposure must precede the outcome.  The severity of the outcome must increase in proportion to the severity of the risk.  

What are the results?
Studies of risk often produce results in terms of Relative Risk or Odds Ratios.  These are discussed further in the Important Concepts section for harm.  The precision of the estimates is measured by confidence intervals .

Will the results help me in patient care?
In addition to the issues discussed earlier , you need to consider the following issues when dealing with a question of harm.

THERAPY:  Is there, in fact, a way to reduce or cure the results of the exposure?

BENEFITS:  Does the magnitude of the risk justify reducing exposure?  Are there adverse effects of reducing exposure?

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

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