Types of Evidence

In this tutorial you will be exposed to many types of evidence that can be used to guide decisions about patient care. Not all types of evidence are equal; some types are considered stronger than others. Many schemas have been proposed to rank the levels of evidence but a consensus or a standard schema has not been reached. For example, the American Nurses Association provides links to 9 different schemas of levels of evidence.

As you continue on with your studies you will learn more about types of evidence, research designs and critical appraisal of the evidence. But for now we will work with a simplified level of evidence pyramid:

The pyramid shows the levels of evidence, with the highest/strongest levels of evidence near the top and the weaker levels of evidence at the bottom. So for example the strongest types of evidence are considered evidence based summaries of topics and Clinical practice guidelines, while opinions are considered the weakest form of evidence, if they are considered a type of evidence at all.

Experts on EBP (evidence based practice) recommend that when searching for evidence to guide patient care, a search for the highest levels of evidence is carried out first. If no evidence exists for your PICO question at the highest levels you move down the pyramid until you locate evidence that addresses your PICO question

Now we will look at each of the types of evidence included in the pyramid.

Research Article

Individual research studies are the foundation of evidence based practice. This video (1:23 minutes) will describe the purpose and content of a research article.

This video will show an example of a research article, describing its characteristics:

To test your understanding of a research article, scan through each of the articles below and make a list of reasons why each is a research article:

Physical activity in pregnancy: a qualitative study of the beliefs of overweight and obese pregnant women

A longitudinal study of alcohol use and antisocial behaviour in young people

Comparison of the effects of salmeterol/fluticasone propionate with fluticasone propionate