Epidemiology chap 8-12 Quizzes for Exam

Assuming that the sample table is for a cohort study, define the risk difference or attributable risk:

(A/A+B) - (C/C+D)

The population etiologic fraction of disease due to smoking is:

0.83 for lung cancer and 0.18 for coronary thrombosis

Still using the information from previous question, among smokers, the etiologic fraction of disease due to smoking is:

0.90 for lung cancer and 0.29 for coronary thrombosis

The death rate per 100,000 for lung cancer is 7 among non-smokers. The death rate per 100,000 for coronary thrombosis is 422 among non-smokers and 599 among smokers. The prevalence of smoking in the population is 55%. The relative risk of dying for a smoker compared to a non-smoker is:

10.1 for lung cancer and 1.4 for coronary thrombosis

What is the specificity of the screening test?

70

A screening examination was performed on 250 persons for Factor X, which is found in disease Y. A definitive diagnosis for disease Y among the 250 persons had been obtained previously. The results are charted below: RESULTS OF DIAGNOSIS SCREENING RESULTS Disease Present Disease Absent Positive for Factor X 40 60 Negative for Factor X 10 140 What is the sensitivity of the screening test?

80

Respect for Persons

All individuals have the right and autonomy to make their own decisions

For human research to be ethical, it should be:

All of these

Surgeons at Hospital A report that the mortality rate at the end of a one-year follow-up after a new coronary bypass procedure is 15%. At Hospital B, the surgeons report a one-year mortality rate of 8% for the same procedure. Before concluding that the surgeons at Hospital B have vastly superior skill, which of the following possible confounders would you examine?

All of these

Which of the following is NOT a requirement of informed consent?

All of these are required

Phase III

Assess the efficacy of the drug in a large sample of volunteers from the target population, using randomization of participants to intervention and control arms.

The Tuskegee Syphilis Study told participants that they were being treated for what?

Bad blood

Which of the following is not a method for controlling the effects of confounding in epidemiologic studies?

Blinding

What type of intervention design focuses on groups or community outcomes?

Community trials

A test that determines whether disease is actually present is a:

Diagnostic test

Regarding the RR reported above, which statement is correct?

Exposure to vitamin A appears to protect against morbidity and mortality for measles.

Confounding and effect modification are the same concepts

False

Intervention designs involve only controlled clinical trials.

False

Odds ratio is the ratio of the risk of disease among the exposed to the risk among the unexposed.

False

Participation in a research study is never voluntary.

False

Population-based cohort studies permit investigations of exposures that are uncommon.

False

Sensitivity refers to the ability of a screening test to identify only nondiseased individuals who actually do not have the disease.

False

Specificity refers to the ability of a screening test to correctly identify all screened individuals who have a disease.

False

The team attributable risk is defined as the ration of the incidence of a disease among exposed individual to the incidence among non-exposed individuals

False

A research protocol is considered exempt if it meets which criteria?

No risk to study participants

A five-year prospective cohort study has just been completed. The study was designed to assess the association between supplemental vitamin A exposure and mortality and morbidity for measles. The RR for incidence of measles was 0.75 and the RR for measles mortality was 0.5.

One of the problems that this study may have faced is individuals lost to follow-up during the five-year period.

Phase IV

Post-marketing research to gather more data about risks and benefits of the drug.

In a study to determine the incidence of a chronic disease, 150 people were examined at the end of a three-year period. Twelve cases were found, giving a cumulative risk of 8%. Fifty other members of the initial cohort could not be examined; 20 of these 50 could not be examined because they died. Which source of bias may have affected the study?

Selection bias: survival bias

On the basis of the relative risk and etiologic fractions associated with smoking for lung cancer and coronary thrombosis, which of the following statements is most likely to be correct?

Smoking seems much more likely to be causally related to lung cancer than to coronary thrombosis

Beneficence

Study participant's physical, mental and social well-being outweighs the importance of new knowledge/scientific advances, personal and/or professional interests

Who is blinded in a single-blinded design?

Study subject

Phase II

Testing group of 100-200 subjects from the target population to examine response and clinical reactions to the drug.

Phase I

Testing response to the drug in a small-scale study of adult volunteers, typically fewer than 100, and identifying maximum tolerated dose.

A new antibody test detects serum antibodies against virus X (sensitivity 99%, specificity 90%). When applied in a group of hospitalized patients diagnosed as having virus X infections, the test is found to have a positive predictive value of 85%. When used to screen a group of healthy blood donors for virus X infections, the test is found to have a positive predictive value of 30%. Which of the following best explains this difference between the positive predictive values?

The prevalence of virus X infection is higher among the hospital patients.

A study is externally valid, or generalizable, if it allows unbiased inferences to the target population.

True

Clinical trials enroll individual subjects and enable randomization of subjects to receive or not receive the intervention.

True

Cohort studies preserve the temporality of cause (exposure) happening before the effect (disease)

True

Federal regulations are established that are designed to standardize the ethics review and monitoring process for researchers, research institutions, and federal funding agencies.

True

For informed consent to begin, study participants should have sufficient time to consider participation (usually 24 hours).

True

Internal validity refers to the accuracy of comparisons made between study groups in epidemiologic research.

True

Reliability refers to the ability of a measuring instrument to give consistent results on repeated trials, regardless of its accuracy.

True

Survival curves may be used to portray patients' survival in clinical studies.

True

The p-value indicates the probability that the finding observed could have occurred by chance alone

True

The population etiology fraction is a measure of the proportion of the disease attributable to the exposed of interest. This measure of effect is influenced by the relative risk of the disease in exposed individuals versus unexposed individual and the prevalence of the exposed in the population

True

The purpose of double-blinding in clinical trials is to reduce errors that results from subjects' knowledge of their assignment to study conditions and the way in which the outcome is assessed.

True

The purpose of matching in a case-control study is to select the controls in such a way that the control group has the same distribution as the cases with respect to certain confounding variables.

True

The term attributable risk is also known as the rate difference or risk difference

True

Validity is the ability of a measuring instrument to give a true measure.

True

Sensitivity and specificity of a screening test refer to its:

Validity

A major advantage of community trials is that they are:

able to estimate directly the realistic impact of behavior change

Lead time bias is best described as:

an apparently longer survival time among persons identified during a screening program because they were identified at an earlier stage of their disease

If it is acceptable that an observed association is a causal one, an estimate of the impact that a successful preventive program might have can be derived from

attributable risk

Cohort study is to risk ratio as:

case-control study is to odds ratio

Subjects for an exposure-based cohort study would be selected most appropriately from:

certain occupational groups such as battery workers

An example of passive follow-up in cohort studies is:

collection and maintenance of data by the federal government

An epidemiologic experiment is performed in which one group is exposed to a suspected factor and the other is not. All individuals with an odd hospital admission number are assigned to the second group. The main purpose of this procedure is to:

improve the likelihood that the two groups will be comparable with regard to known and unknown confounding factors.

You are investigating the role of physical activity in heart disease and suggest that physical activity protects against having a heart attack. While presenting these data to your colleagues, someone asks if you have thought about confounders such as factor X. This factor X could have confounded your interpretation of the data if it:

is a factor associated with physical activity and heart disease.

Justice

requires fairness in distribution of the benefits and burdens of research

The strategy which is not aimed at reducing selection bias is:

standardized protocol for structured interviews

A major advantage of cohort studies over case-control studies with respect to the role of a suspected factor in the etiology of a disease is that:

they permit direct estimation of risk of disease in those exposed to the suspected factor.