When was this source published?
How old are the references and data used?
Has this source, or its data, been updated?
Does this type of information get updated?
Is there likely to be more recent information available elsewhere?
Is this information relevant to your assignment? Is there likely to be better information?
Is this aimed at the correct audience?
Who wrote it? What are their qualifications?
Where do they work? Who do they work for?
Are they likely to have a good understanding of this field?
Is the information reliable?
Can you find the original source?
What is the quality of the presentation? Are there significant errors?
Do the conclusions match the data?
Have all sides been considered?
Why has the article been written?
Is there any obvious bias? Is the author or their employer likely to get a benefit out of the recommendations?
Is it recommending a particular course of action or therapy? Does the data support this? Are any alternatives considered?
When answering clinical questions, you need to use the highest level of evidence possible. In the diagram below, evidence that is higher up the pyramid is of higher quality i.e., systematic reviews (secondary research).
Secondary research appraises the quality of original research studies, summarises the findings, and often makes recommendations for practice. However, secondary research is not always available, and searching for primary research such as randomised control trials may be required.
| Secondary research | Primary research |
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| Secondary study-type examples | Primary study-type examples |
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Checklists Use the following checklists to help decide if an article is primary or secondary research. |
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In secondary research, you will probably see:
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In primary research, you will probably see:
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A systematic review is regarded as a high level of evidence and is secondary research. It starts with a specific and answerable clinical question, identifies all the research available and eliminates flawed and low-quality studies, then uses the results of the remaining high-quality studies to answer the clinical question and thus make recommendations on best practices.
Randomised controlled trials are primary research. Researchers assign participants randomly into an intervention group or a control group, then results are compared to see if the intervention had an effect.
A cohort study is primary research. It looks at the health outcomes of a specified group, comparing people in the group who have been exposed to a potential risk factor with those who have not been exposed, and looks for links and correlations.
Case control studies looks at existing data to compare people who have a specific health outcome or condition, compared with those who don't, to find what factors differ between the groups.
Case series and case reports look at one or more individual cases and outcomes or responses to interventions. Regarded as a low level of evidence, the information might not apply to a wider population.
Editorials and expert opinions can be based on a practitioner's individual experience. Generally regarded as one of the lowest levels of acceptable evidence, they do not necessarily account for uncontrolled external factors, differences between different groups, nor placebo effects.
Hover over each level of the evidence pyramid for more detail
To learn more about levels of evidence, click on the links below:
Use the arrows at the right and left of the box below to click through and see the characteristics of a number of different study types from the levels of evidence pyramid.
