Question

A study was conducted to test whether use of antibiotics protects against the risk of a first-time heart attack (myocardial infarction). Patients diagnosed with a first-time myocardial infarction between 1992 and 1997 were identified from 350 general practices in the United Kingdom. For each patient diagnosed with a first-time myocardial infarction, 4 patients with no history of myocardial infarction who were the same age and sex were selected from the patients of the same general practices. For all study participants, prescriptions for antibiotics during the previous three years were assessed from the patient's medical records. Compared to patients with no myocardial infarction, patients diagnosed with a first-time myocardial infarction were less likely to have used specific antibiotics (i.e., tetracyclines and quinolones).

1. What type of study design is this? (Choose the one best answer)

a. ecologic

b. case series

c. cross-sectional

d. case-control

e. cohort

f. randomized trial

Investigators implemented a study to see if estrogen reduces the risk of subsequent coronary heart disease (CHD) events in women who have been diagnosed with coronary heart disease in the past. A total of 2,763 women who had coronary heart disease were recruited to participate in the study. Each participant was randomly assigned to receive either estrogen or placebo to take every day. After 4 years of follow-up, those taking estrogen had an almost identical risk of having a myocardial infarction or dying from CHD as those taking the placebo.

2. What type of study design is this? (Choose the one best answer)

a. ecologic

b. case series

c. cross-sectional

d. case-control

e. cohort

f. randomized trial

Answer 1

1.(b) A case series (also known as a clinical series) is a type of medical research study that tracks subjects with a known exposure, such as patients who have received a similar treatment, or examines their medical records for exposure and outcome.

2.(f) The terms "RCT" and randomized trial are sometimes used synonymously, but the methodologically sound practice is to reserve the "RCT" name only for trials that contain control groups, in which groups receiving the experimental treatment are compared with control groups receiving no treatment (a placebo-controlled study.