Further down the pyramid


RCTs, cohort studies, and case-control studies are among the most useful study designs for systematic reviews.

But what if these studies aren’t available, or maybe there aren’t enough of these types of studies to do a comprehensive analysis? That’s when you go further down the pyramid of evidence to non-comparative research.

Non-comparative research is a broad category, describing any type of study that doesn’t compare an intervention group with a control group.

Types of non-comparative research:

Case studies: describe the symptoms, diagnosis, treatment and follow up for a group of patients who all have the same exposure or treatment.

Case reports:  tell the detailed story of an individual patient, describing that person’s symptoms, diagnosis, treatment and follow-up. Case reports often describe situations that are rare or unexpected.

When to include: These studies could be useful if you’re interested in safety issues or a rare condition/outcome. Although case reports don’t offer a comparison with other interventions, they can give you insight into the safety of a specific treatment.

Now that you know about all of your study options, it’s time to choose the study types you want to include in your systematic review.