Clinical Reasoning Tutorial Part 2

Welcome!

Welcome to the second part of your Clinical Reasoning tutorial. Here, we'll talk about the different types of study designs and what that means for the information you'll be finding through the library search engine.

We talked in our last tutorial about how you can't trust some information on the web. When it comes to our library resources, you can typically trust the information you find there but it may not be suitable for your patient question.

Evidence Pyramid

On this page click the link on the left that says "Identify a study design."

The first thing I'll show you is the evidence pyramid. This pyramid lists all the different types of sources and stacks them up. The ones at the top are considered the highest forms of evidence and the most trustworthy. 

You should strive to use sources at the top of the pyramid, though there may be situations where you have to use other evidence which ranks lower on the pyramid. 

Systematic Review

You'll notice that a systematic review is at the top of pyramid. 

A systematic review is different from the other studies on the pyramid because it is not a study at all, but a literature review.

A group of researchers create a question and search through existing studies for an answer to their question.

Systematic reviews do the legwork for you by searching through the evidence in PubMed and other resources. It is the highest quality evidence because it summarizes multiple studies.

A meta-analysis is an optional component of a systematic review which crunches the numbers of the results in each study and comes up with an aggregate result.

Randomized Controlled Trial

 A randomized controlled trial is an experiment conducted using two groups: a control and an intervention group. The intervention is given a treatment for a disease, while the control group is given a different treatment or no treatment at all.

 Example: Researchers test a binocular iPad game versus patching for the treatment of amblyopia to see which treatment is more effective

Cohort Study

 A cohort study looks forward in time (meaning it is prospective). It examines a population that does not have a disease over a period of time to see who develops that disease. It looks at an exposure (like, saying, smoking) and tries to trace it to an outcome (lung cancer).

 Example: A group of Medicare beneficiaries with a diagnosis of cataracts were analyzed from 2002 to 2012. Surgery for cataracts decreased mortality incidence.

Case-Control Study

 A case-control study looks backward in time (meaning it is retrospective). This type of study looks at a group of patients with a disease and matches them to a group of patients without a disease (the control group) to try and identify exposures and outcomes.

Example: Researchers look through the medical records of a group of patients with lung cancer to figure out how many participants were smokers.

Case Study

 A case study documents one patient's (typically unusual) features of a disorder. You may find if you've been assigned a rare disorder like retinitis pigmentosa that you can only find case studies on your topic. That is because there simply aren't enough patients with the disease to conduct a larger study like a randomized controlled trial.

Cross-Sectional Study

A cross-sectional study looks at a group of diseased and non-diseased people at one point in time or over a short period of time. It usually measures the prevalence of a disease, typically by administering a survey.

Example: Researchers surveyed 16 ophthalmology departments of hospitals, asking 220 patients with allergic conjunctivitis about their comorbidities and the time and length of their allergy episodes.

Abstract Quiz

Click the link that says "Identify a study design [quiz]." The following are abstracts that can be found in PubMed. Take a moment to answer the following questions.

 

 

Certificate

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