Review Question - QID 218769

This study seeks to evaluate the efficacy of an intervention compared to the current standard of care for reducing PJI incidence after hip arthroplasty by screening for glycemic control in patients with diabetes. Because the study includes randomization of participants into an intervention arm consisting of the new screening strategy and a control arm consisting of the current standard of care, this design is best described as a randomized, controlled trial.

Randomized, controlled trials are the gold standard of interventional studies in evidence-based medicine. By randomizing participants into cohorts that receive different interventions, researchers are able to control for all observed and unobserved confounding variables. Through the randomization process, confounding variable balance is, by definition, achieved in the trial arms. The only residual difference between the trial arms is the intervention itself; thus, any difference in outcomes between the arms can be directly attributed to the causal effect of the intervention. The control group for randomized trials typically receive the current standard of care or a placebo. In well-designed randomized controlled trials, trial investigators, analysts, and patients are blinded to which cohort the patients were assigned to, to reduce the risk of observer and participant bias. However, in some cases this is not technically or ethically possible. While randomized, controlled trials are considered the gold standard for medical evidence, it is not always feasible or ethical to conduct a randomized trial. For example, it would not be ethical to conduct a trial on whether smoking cigarettes increases all-cause mortality.

Incorrect Answers:
Answer 1: Case-control studies are observational studies in which cohorts are created based on the outcome of interest. Investigators then compare the exposure histories of the cohorts to determine whether the prevalence of a certain exposure is increased in either of the cohorts. An example of a case-control study would be if researchers identified patients with a PJI after hip arthroplasty and patients without a PJI after hip arthroplasty. They could then compare whether poor glycemic control was present preoperatively in these 2 cohorts.

Answer 2: Crossover studies are a type of randomized, controlled study with an additional step. The additional step consists of cohort “crossing over” during the course of the study such that patients receiving the intervention are switched to the current standard of care or placebo after a washout period, and vice versa. In this way, each cohort can serve as its own control in the analysis. An example of a crossover trial would be if researchers studying a novel drug randomized patients into an intervention and placebo arm and midway during the trial, patients who were receiving the novel drug were switched to placebo and vice versa.

Answer 3: Meta-analysis is a statistical technique used to combine the results of multiple observational or interventional studies. By pooling the results of multiple studies, increased statistical power can be achieved to detect small but statistically significant effects. Meta-analyses can also provide a measure of the degree of publication bias that exists for a particular question.

Answer 4: Prospective cohort studies create cohorts of patients based on an exposure and follow these patients longitudinally until they develop a certain outcome of interest. The crucial difference between prospective cohort studies and randomized controlled trials is that in the former, participants are not randomly assigned to receive the exposure unlike in randomized controlled trials.

Bullet Summary:
Randomized controlled trials are characterized by the randomization of participants to receive an intervention, which controls for observed and unobserved confounding variables.