Nursing LibGuides Reusable Resources: EBP

Clinical practice guidelines are systematically developed statements to assist practitioner and patient decisions about appropriate health care for specific clinical circumstances. (Institute of Medicine definition)

"Systematic reviews are studies of studies, with explicit methods to identify, select, critically appraise, and summarize the results of all studies that are relevant to a clearly defined question. The definition of a meta-analysis is much narrower, referring to the statistical methods that are used to combine the results from different studies." From Systematic reviews and meta-analyses of randomized trials: principles and pitfalls in the European Heart Journal.

"A controlled trial means that study participants are split into two groups: One group is given the treatment and the other (the control group) is not. The control group may be given a placebo that mimics the actual treatment, but does not contain the treatment being tested.

For example, a sugar pill or an injection of saline solution may be used instead of a dose of the drug. This ensures the only meaningful difference between the two groups is whether they received the treatment or not. The control group helps researchers learn what would have happened to the treatment group if they hadn’t received the treatment. For example, some patients may recover on their own. Researchers need to know how often this happens, so they don’t attribute all recoveries to the effect of the treatment.

Study participants are randomly assigned to one group or the other, a process similar to a coin toss. Just as a coin toss is equally likely to end up heads or tails, study participants are equally likely to end up in the treatment or the control group. With enough study participants, this results in two groups that closely resemble each other. The only difference is that one group got “heads” while the other got “tails.”

The randomization of randomized-controlled trials with large enough samples ensures that all possible differences are accounted for, even those that may not be observed, such as genetic traits. If the treatment and control groups are similar at the start of the study but end up with different outcomes, the treatment is the most likely cause. The randomized-controlled trial allows researchers to rule out alternative explanations."

From "What is a clinical trial? A health policy expert explains" in Credo Reference.

Cohort studies take a group of people who are in some way similar, either in experience or in characteristics. For instance, a cohort may be as simple as a group of students in the same year and district, or as complex as all patients who had appendectomies at a particular hospital during a two year period. Cohort studies are prospective. Cohorts are chosen, and then an intervention is introduced. They do not have the randomization of randomized-controlled trials. From Cohort Design in the Encyclopedia of Nursing Research in Credo Reference.

"A retrospective epidemiological study in which subjects who have contracted a particular disease (the ‘cases’) are compared with similar subjects who did not contract the disease (the ‘controls’). The term disease is often used quite liberally to include such things as having an abortion or failure to follow a prescribed regimen of medication. The cases and the controls are often matched on one or more variables that might otherwise confound the comparison." Note that these are retrospective not prospective, so there can be many confounders. From Dictionary of Nursing Theory and Research in Credo Reference.

Case series and case reports report on a person or group of people who recieved a treatment or intervention, or on a specific incident or event. They do not compare to a control, so they are informative but not experimental or quasi-experimental.

Animal studies are done to test out concepts in new areas, such as testing that a new compound isn't outright poisonous or toxic. Lab studies, also called in vitro or cell culture, test very preliminary concepts, such as if it is possible for a compound to even effect targets at all. In vitro is from Latin, for "in glass", referring to test tubes.