Epi Study Design Exam 2 Examples

Uncontrolled Observation

Four rats in one cage were found dead at the university animal colony. In the adjacent cage, one rat convulsed and dies, two rats became ill but survived, and one rat was ill. The veterinarian declared that an epizootic was present.

Cohort Study

1500 adult males working for Lockheed Aircraft were initially examined in 1951 and were classified by diagnosis criteria for coronary artery disease. Every 3 years they have been examined for new cases of this disease; attack rates in different subgroups have been computed annually.

Case-Control Study

100 patients with infectious hepatitis and 100 matched neighborhood well controls were questioned regarding a history of eating raw clams or oysters within the preceding 3 months.

Cross-Sectional or Prevalence Study

Questionnaires were mailed to every 10th person listed in the city telephone book. Each person was asked to list age, sex, smoking habits, and respiratory symptoms during the preceding 7 days. Over 90% of the questionnaires were completed and returned. Prevalence rates of upper respiratory symptoms were determined from the response.

Cross-Sectional or Prevalence Study

In 1997 a sample of 3500 National City residents were recruited into a study. Each subject was asked about their current sexual behavior and each person's medical record was reviewed for diagnosis of chlamydia at the time of enrollment in 1997.

Cohort Study

At the beginning of boot camp, the recruit's shoes were classified. Each recruit was tracked for the occurrence of stress fracture during training.

Case-Control Study

A group of recruits that got stress fractures during training were asked to describe their shoes at the beginning of training. A group of recruits without stress fractures were asked to do the same thing.

Cohort Study

In a study begun in 1965, a group of 3000 cancer free adults in San Diego were asked about smokeless tobacco use. The occurrence of cases of cancer was studied in this group between 1981 and 1995. What type of study is this?

Case Control

A study looked at the relationship between menstrual factors and breast cancer in African-American women. Through a well-known national cancer registry, we identified 304 African-American women, aged 20-64 living in three Tennessee counties, diagnosed with breast cancer between 1995 and 1998. A comparison group of 305 was selected through random-digit dialing. Phone interviews with both groups of women were then conducted to illicit information on menstrual factors- age at menarche, time to regularity, cycle length, flow length, age at menopause- and other risk factors. What is the design of this study?

Cross-Sectional

H. pylori infection is related to several gastroduodenal diseases, though the route of transmission remains unclear. 695 healthy people participating in a health checkup program at the UCSD Medical Center were enrolled in a study to examine factors associated with H. pylori infection. On the day of their clinic visit, H. pylori status was determined and data on other factors known or suspected to be related to infection status was collected using a questionnaire. What is the design of this study?

Cross-Sectional

A study was conducted to evaluate whether body weight affects the risk of incident childhood asthma. 9,828 children aged 6-14 years were sampled from every county in Delaware in 1994. They were evaluated at enrollment and classified based on body-mass index (BMI) as being overweight or not. The children were then also examined to determine the amount of asthma. What is the design of this study?

Retrospective Cohort

In 2000, investigators identified from the institute's health database a total of 11,104 older (>65 yrs) non-diabetic subjects who were residents of long-term care institutions in Ontario, Canada during 1990. These subjects were classified based on whether or not they received neuroleptic agents. Development of diabetes in these subjects between 1990 and 2000 was determined from pharmacy records and measured by newly prescribed anti-diabetic drug therapy. What is the design of this study?

Case-control

What is the best study design for studying rare diseases?

In choosing controls for a case-control study, the most important factor to consider is:

That the controls come from the same source population as the cases

Prospective Cohort

What is the study design that is the least economical?

Prospective and Retrospective Cohort

Which study design is longitudinal in nature?

Number of exposures can be studied simultaneously

In a cohort study, the advantage of starting by selecting a defined population for study before any of its members become exposed, rather than starting by selecting exposed and nonexposed individuals is:...?

Cross-sectional study

Residents of 3 villages with 3 different types of water supply were asked to participate in a survey to identify cholera carriers. Because several cholera deaths had occurred recently, virtually everyone present at the time underwent examination. The proportion of residents in each village who were carriers was computed and compared. What is the proper classification for this study?

Case-control study example

Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or exposure under study.