Evidence 101: Q&A with an expert

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Dr. David Streiner has attempted to retire three times, but this biostatistics expert is in high demand.

Dr. David Streiner headshot
Dr. David Streiner


Having trained as a clinical psychologist more than 50 years ago, Dr. Streiner is now Professor Emeritus in both the Department of Psychiatry and Behavioural Neurosciences and the Department of Clinical Epidemiology and Biostatistics at McMaster University, and a Professor in the Department of Psychiatry at the University of Toronto.

His research expertise is sought by scientists, faculty, residents, and students alike. A star behind the scenes, Dr. Streiner frequently consults with HRI scientists and trainees on everything from study design to research analysis.

In this question-and-answer feature, Dr. Streiner provides clarity about some of the most common questions we receive at HRI about evidence.

What does “evidence” mean in the context of healthcare?

Evidence is the available body of facts that healthcare providers can draw from to best treat patients. The most common method of obtaining healthcare evidence today is through research studies. Prior to the rise of scientific healthcare research, evidence was based primarily on clinical expertise and opinion.

What is “evidence-based practice” in healthcare?

The term “evidence-based practice” originated from Dr. David Sackett, an American-Canadian physician who defined the term as “…the conscientious, explicit, and judicious use of the current best evidence in making decisions about the care of patients.”

So when using an evidence-based approach, one would base healthcare decisions solely on evidence from scientific research.

How is “evidence-informed practice” different from “evidence-based practice”?

Early critics of evidence-based practice argued that its definition limited medicine to a “cookbook approach” that fails to consider each patient’s unique values and preferences, and downplays the clinician’s experience and knowledge of the patient. A new term began to circulate, which encompassed a more person-centred approach:  evidence-informed practice.

Over time, the concept of evidence-based practice has evolved to include not only scientific research but also clinical expertise and the patient perspective brought to light by proponents of evidence-informed practice. Today, we see both terms used interchangeably.

How do we create evidence in healthcare?

First of all, we need research. Without research, we have no evidence. But to do research, we also need participants. We know that research plays a central role in designing and evaluating new treatments, but we often forget that patients and families play a central role in the research itself.

When answering research questions, we use a variety of methodologies. For example, if we want to know about the prevalence of a medical condition in a population, a cross-sectional study would be appropriate. On the other hand, if we want to find out whether a proposed treatment would help people with a specific condition, a randomized controlled trial would be used. At the end of the day, the research methodology depends on the question being asked.

The following infographic outlines some of the most common research approaches used at HRI:

Infographic explaining several types of research studies