Review Question - QID 104024

The researcher used a cross-sectional study design by measuring both the exposure (vaccination) and the outcome (autism spectrum disorder diagnosis) simultaneously.

Cross-sectional studies are a commonly used tool in epidemiology and medical literature. The defining characteristic of these studies is that exposure and outcome are measured simultaneously. This creates the so-called "snapshot." While cross-sectional studies are useful for revealing associations and identifying possible risk factors, the simultaneous measurement of exposure and outcome means that causation cannot be derived from a cross-sectional study.

Mann reviews several observational study designs. He notes that these studies are frequently used due to their practicalness, and that cross-sectional studies are best suited to determine prevalence, case-control studies are useful for studying rare diseases/outcomes, and cohort studies are frequently used to study incidence, risk factors, and prognosis.

Sedgewick discusses crossover trials (also known as case-crossover trials). He notes that crossover trials are defined by having "within subject" design, where subjects function as their own controls. This allows for treatment and "control" groups to have the same baseline characteristics. These trials are often employed in the setting of chronic problems and short interventions (e.g. new pain regiment for chronic pain patients).

Illustration A is a schematic of the construction of a cross-sectional study. Illustration B demonstrates the difference between case-control and cohort studies.

Incorrect Answers:
Answer 2: In a case-crossover study, subjects serve both as controls and cases over time.
Answer 3: In a cohort study, a group of individuals is followed over time (either prospectively or retrospectively) for the development of the outcome of interest.
Answer 4: In a randomized controlled trial (RCT), subjects are randomly selected to different interventions.
Answer 5: In a case-control study, cases (individuals with disease) and controls (individuals without disease) are separately identified and exposures are measured for both groups.