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NURS 7301 - Methods for Evidence Based Practice: Evidence Based Practice

Defining EBP

Evidence-Based Practice (EBP) is the framework for your clinical decision-making process. It is the integration of

  • your knowledge, skills, and past experience (Clinical Expertise);
  • the unique preferences, concerns and expectations of your patient (Patient Characteristics); and
  • valid and clinically relevant research (Best Evidence)



5 A's - EBP Process


      - Review the Situation (Assess)

     - Define the clinical problem as a question (Ask)

     - Select resources, design a strategy, & search for the

       answer (Acquire)

     - Summarize the evidence yield (Appraise)

     - Apply the evidence (Apply)

Types of Clinical Questions

Question Type Question Frame Study Type
Diagnosis Which test is best to differentiate between those with and without a disease? Think sensitivity and specificity. Prospective, blind comparison to a gold standard; Cross-sectional
Etiology/Harm What is the cause of the disease or condition? What are the effects of potentially harmful agents on the patient? RCT; Case-control; Cohort
Prevention What is the best type of early screening? What risk factors need to be identified and modified in in order to reduce the chance of developing the disease? Systematic Review; RCT
Prognosis What is a patient's likely course over time due to factors other than the intervention? Cohort
Therapy What is the best treatment? Systematic Review; RCT

Adapted from: Sackett, D.L. & Livingstone, C. (2000). Evidence-based Medicine: How to practice & teach EBM.

Study Types

Study Type Description

An empirical study used to estimate the causal impact of an intervention on its target population without random assignment. It shares similarities with the traditional experimental design or randomized controlled trial, but it specifically lacks the element of random assignment to treatment or control.

Case Control Studies

Studies in which patients who already have a specific condition are compared with people who do not have the condition. The researcher looks back to identify factors or exposures that might be associated with the illness.  They often rely on medical records and patient recall for data collection. These types of studies are often less reliable than randomized controlled trials and cohort studies because showing a statistical relationship does not mean than one factor necessarily caused the other.

Case Series/Case Reports Consist of collections of reports on the treatment of individual patients or a report on a single patient. Because they are reports of cases and use no control groups to compare outcomes, they have little statistical validity.
Cohort Identify a group of patients who are already taking a particular treatment or have an exposure, follow them forward over time, and then compare their outcomes with a similar group that has not been affected by the treatment or exposure being studied. Cohort studies are observational and not as reliable as randomized controlled studies, since the two groups may differ in ways other than in the variable under study.  
Cross-Sectional Describe the relationship between diseases and other factors at one point in time in a defined population. Cross sectional studies lack any information on timing of exposure and outcome relationships and include only prevalent cases.  They are often used for comparing diagnostic tests.  Studies that show the efficacy of a diagnostic test are also called prospective, blind comparison to a gold standard study. This is a controlled trial that looks at patients with varying degrees of an illness and administers both diagnostic tests — the test under investigation and the “gold standard” test — to all of the patients in the study group. The sensitivity and specificity of the new test are compared to that of the gold standard to determine potential usefulness.
Meta-Analysis Thoroughly examines a number of valid studies on a topic and mathematically combine the results using accepted statistical methodology to report the results as if it were one large study.
Qualitative Research Answers a wide variety of questions related to human responses to actual or potential health problems.The purpose of qualitative research is to describe, explore and explain the health-related phenomena being studied.
Randomized Controlled Trials (RCTs) Carefully planned experiments that introduce a treatment or exposure to study its effect on real patients. They include methodologies that reduce the potential for bias (randomization and blinding) and that allow for comparison between intervention groups and control (no intervention) groups.  A randomized controlled trial is a planned experiment and can provide sound evidence of cause and effect.  
Retrospective or Historical Cohort Follows the same direction of inquiry as a cohort study.  Subjects begin with the presence or absence of an exposure or risk factor and are followed until the outcome of interest is observed.  However, this study design uses information that has been collected in the past and kept in files or databases.  Patients are identified for exposure or non-exposures and the data is followed forward to an effect or outcome of interest.
Systematic Review Focuses on a clinical topic and answers a specific question. An extensive literature search is conducted to identify studies with sound methodology. The studies are reviewed, assessed for quality, and the results summarized according to the predetermined criteria of the review question.

Hierarchy of the Evidence

Research design and evidence

By CFCF (Own work) [CC BY-SA 4.0 (], via Wikimedia Commons

AACN Levels of Evidence

AACN new levels of evidence

AACN Levels of evidence citation

Process Flow

EBP Acquiring Evidence steps