SECONDARY LITERATURE analyzes, synopsizes, and synthesizes the primary literature.
The advantage of secondary literature is that the information has already been appraised by others. The Publication Types Evidence Pyramid (to the right) is designed so the most believable evidence is at the top of the pyramid. The tapering of the pyramid also points out there is less of this high quality information available.
reports original scientific research.
If you have not been able to find pre-appraised information then you will have to appraise the validity of the primary literature yourself.
Look at the introduction or methods section to discover a sentence which states the question investigated in the paper. Does it address all the elements of your question, or only portions?
The methods section should allow you to find the publication type, a description of the patients included and excluded from the study, and the number of patients studied. The greater the similarity between your patient and the patients studied, the more likely the results apply to your patient.The greater the number of patients studied, the more likely the results of the study will be significant.
The results section of the study should provide numbers so you may make some simple calculations. The calculations will add to your conclusions about the validty of the results of the study.
The discussion may contain notes about the limitations of the study, interpretation of the results of the study, ideas about areas of future study.
There are two forms of error that can cause the results of a study to be false. Random Error is analagous to the idea that if you flip a coin 10 times you may likely end up with a result that is not 5 heads and 5 tails. If you flip a coin 1,000 times the results are likely to be very close to 500/500. Systematic Error (also called Bias) is due to some flaw in the design, implementation, or analysis of a study. This is why looking at the methods section carefully is important.
Now that you have appraised the evidence, continue on to Step 4: Apply, Assess, and Research.
Critically-appraised journal articles