Question

Descriptions of each major types of epidemiologic study:

- randomized controlled trial,

- cohort,

- case-control

Strengths for 2 Strengths

weaknesses 2 weaknesses

Answer 1

Randomized controlled trial: It is a clinical trial in which persons are randomly assigned to exposure or treatment groups. In this study we compare two or more groups of people. One of the group called a participant or subject group receive a new treatment, and other group called control group receive the current standard treatment (existing treatment, no treatment or a placebo).

Strength

(1) Randomized controlled clinical trials (RCTs) are considered most reliable for ascertaining the efficacy and safety of a treatment. It can demonstrate the superiority of a new treatment over an existing standard treatment or a placebo.

(2) It decreases selection bias and minimizes since it allows the specific allocation and administration of intervention to a chosen population.

Weakness

(1) It is not resource efficient as it has high cost.

(2) results may not always mimic real-life treatment situation.

Cohort study: in cohort study, we record whether study participants are exposed or not, and then tracks the participants to see if they develop the disease of interest. It is an observational study where we observe rather than determines the participants exposure status. While comparing the disease rate in the exposed group with the disease rate in the unexposed group (comparison group), if the disease rate is significantly different in the exposed group, the exposure is associated with illness.

Strength

(1) Since subjects are known to be disease-free at the beginning of the observation, cohort study clearly indicates the temporal sequence between exposure and outcome.

(2) Cohort studies allow to calculate the both absolute and relative risk incidence of disease in exposure groups,

Weakness

(1) The lengthy follow-up makes it unsuitable for quickly response to a public health concern such as an outbreak.

(2) They are not good for rare diseases.

Case-control study: In a case-control study, we start by enrolling a group of people with disease (case-patients/group) and group of people without disease (comparison group). Then previous exposures between the two groups is compared. If the amount of exposure among the case group is significantly higher than the amount expected based on the control group, then illness is associated with that exposure.

Strength

(1) It is efficient for rare diseases or diseases with a long latency period between exposure and disease manifestation.

(2) It is less costly less time-consuming and easy to conduct which gives it advantage over other analytical study methods.

Weakness

(1) It is subject to selection, recall and observer bias.

(2) Unlike cohort, it does not allow calculation of incidence or absolute risk.