Question

Managerial Epidemiology

When conducting a study, patients occasionally “crossover” to other portions of the study.

List one intervention that may impact the patient after this crossover,

how it might affect the results of the study, and which (if any) precautions need to be considered

when finding crossover data. Additionally, explain a cohort study, and what types of diseases are best to study using a cohort.

Managerial Epidemiology Cases and Concepts - 180 Day Option, 3rd Edition
Steven T. Fleming 2014

Answer 1

It is well known that in crossover designs, each study participant receives all treatments that are being investigated, but at different times. The order in which a study participant receives the treatments is randomized.

For example, patient X is randomized to receive Treatment #01 for a period of time.

After completing Treatment #1, the patient then “crosses over” and receives Treatment #2.

Generally there is a gap period between treatments known as washout when no treatment is delivered.

Finally outcomes are examined during and/or after each treatment.

List of interventions that may impact the patient after this crossover:

Behavior changes

Variability of measured outcomes depending on the behavioral change

Individualized tailoring of the intervention

Different groups or organizational levels targeted by the intervention.

Special precautions have to be considered in crossover studies wash-in and wash-out periods should be appropriate.

Note: if more than two interventions are compared in a crossover study, the latin square design can be used.

The cohort study is an analytical method of epidemiological study in which a subset of population is identified who have been, exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease or outcome.

Cohort studies describe incidence or natural history.

• It analyze predictors (risk factors) hence supporting the calculation of relative risk.

• Cohort studies measure events in temporal sequence hence distinguishing causes from effects.

At the last cohort studies are best fitted for epidemiological diseases study as:

Diabetes, cancer, AIDS etc.