Edward H. Livingston
in
Many readers will read only the abstract of a research article, so it should include as precise a summary of the content as possible. In addition, because readers may decide to review the entire article based on information in the abstract, it should be well written and carefully constructed....
Edward H. Livingston
in
In a
case series
study, observations are made on a series of individuals, before and after they have received the same intervention, exposure, or diagnosis but have no control group. Case series describe characteristics of a group of patients or participants with a particular disease, disorder, signs, or symptoms or a group of patients or participants who have undergone a particular procedure or experienced a specific exposure or event. A case series may also examine larger units, such as groups of hospitals or municipalities. Case series can be useful to formulate a case definition of a disease or describe the experience of an individual or institution in treating a disease or performing a type of procedure. Case series should comprise consecutive patients or observations seen by the individual or institution to minimize ...
Edward H. Livingston
in
Case-control studies
, which are always retrospective, compare those who have had an outcome or event (
cases
) with those who have not (
controls
). Cases and controls are then evaluated for exposure to various
risk factors
and thus should not be selected on the basis of their exposure to the risk factors under investigation. Cases and controls generally are matched according to specific characteristics (eg, age, sex, duration of disease) to reduce ...
Edward H. Livingston
in
The International Committee of Medical Journal Editors (ICMJE) defines a clinical trial as “any research project that prospectively assigns human participants to intervention, with or without concurrent comparison or control groups, to study the relationship between a health-related intervention and a health outcome.”6 All clinical trials must be registered at an appropriate online public registry. Interventions include but are not limited to drugs, surgical procedures, devices, behavioral treatments, educational programs, dietary interventions, quality improvement interventions, process-of-care changes, and the like....
Edward H. Livingston
in
Cluster randomization
is undertaken when performance of the intervention risks contamination of the control group. Imagine a multifaceted intervention that involves sedation protocols and measures of arousal levels and readiness for weaning from a mechanical ventilator in a trial of extubation.25 In this scenario, intensive care unit (ICU) personnel performing these functions may be influenced by the effectiveness of the interventions and consciously or unconsciously use them on patients assigned to the control group. In cases such as this, it is best to perform the intervention in one ICU and apply the control intervention in a separate ICU. Instead of randomizing individual patients to intervention or control groups, ICUs are randomized. Each ICU is considered a cluster of patients....
Edward H. Livingston
in
In a
cohort study
, a defined group of people (the cohort) is followed up over time to examine associations between different interventions and subsequent interventions. Cohort studies may be concurrent (prospective) or nonconcurrent (retrospective). A prospective cohort study follows up a group, or
cohort
, of individuals who are initially free of the outcome of interest. Individuals in a cohort generally share some underlying characteristic, such as age, sex, or exposure to a ...
Edward H. Livingston
in
A
comparative effectiveness
study compares different interventions or strategies to prevent, diagnose, treat, and monitor health conditions to determine which work best for which patients and under what circumstances and which are associated with the greatest benefits and harms. Comparative effectiveness studies evaluate how effective existing therapies are in achieving various clinical outcomes. The outcomes may be tested by conducting RCTs or by observational analysis of existing data. Thus, from a study design perspective, they differ little from conventional studies of clinical efficacy....
Edward H. Livingston
in
Cross-sectional studies
observe individuals at a single point or during a specific interval, in which exposure and outcome are ascertained simultaneously. Such studies may be helpful for suggesting associations among variables but cannot address whether one condition may precede or follow another. Thus, cross-sectional studies cannot establish ...
Edward H. Livingston
in
In a
crossover
trial, participants receive more than 1 of the treatments under investigation, usually in a randomly determined sequence and with a prespecified amount of time (a
washout period
) between sequential treatments. The participants and the investigators are generally
blinded
to the treatment assignment (double-blinded). This experimental design is often used for evaluating drug treatments. Each participant serves as his or her own control, thereby eliminating variability when comparing treatment effects and reducing the sample size needed to detect a statistically ...
Edward H. Livingston
in
Authors should address whether the hypothesis was supported or refuted by the study results or how the study question was answered. The study result should be placed in the context of published literature. The limitations of the study should be discussed, especially possible sources of ...
