HSC 404- Final Exam

What factors comprise the epidemiologic triangle?

-Agent -Host -Environment

The strategies that are aimed at reducing selection bias are:

-Development of an explicit case definition -Encouragement of high participation rates -Enrollment of all cases in a defined time and region

What are the methods for controlling the effects of confounding in epidemiologic studies?

-Randomization -Stratification -Matching -Restriction

What is true concerning attributable risk?

-The rate difference of risk difference between the incidence rate of disease in the exposed group and the incidence rate of disease in the nonexposed group -It is useful measure of public health impact of an exposure

The population etiologic fraction is a measure of the proportion of the disease rate in a population attributable to the exposure of interest

-The relative risk of the disease in exposed individuals versus unexposed individuals -The prevalence of the exposure in the population

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?

-The severity (stage) of disease of the patients at the two hospitals at baseline -The starting point of the one-year follow-up at both hospitals (after operation versus after discharge) -Difference in the post-operative care at the two hospitals -Equally thorough follow-up for mortality

In a survery which uses lay interviewers to interview one person about his or her health and the health of household members the sources of error include:

-the person with disease has had no symptoms and is not aware of the disease -The respondent provides the information but the interviewer doesnt record it or record incorrectly -The interviewer doesnt ask the questions that he or she is instructed to ask, or asks incorrectly -The person has had symptoms and has had medical attention but does not know the name of the disease

Synergism

A situation in which the combined effect of several exposures is greater than the sum of the individual effects

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

Suppose that the population attributable-risk percent in an analysis assessing the relationship between physical inactivity and heart disease was 30% (Assume there is a casual association between physical inactivity and heart disease). Which best defines this results?

Approximately 30% of heart disease is attributed to physical inactivity

If it is accepted that an observed association is a casual one, an estimate of the impact that a successful preventative program might have, can be derived from:

Attributable risk

The purpose of a double-blind study is to:

Avoid observer and interviewee bias

The healthy worker effect

Healthy persons are more likely to gain employment than unhealthy persons

Selective screening involves applying the screening test to which of the following?

High-risk groups

Difference in time between the date of diagnosis with screening and the date of diagnosis without screening, which, if counted in the survival time of patients, will give a misleading picture of the benefits of treatment

Lead-time bias

Slow-progressing cases of disease with a better prognosis are more likely to be identified than faster-progressing cases of disease with a poorer prognosis. Thus, cases diagnosed through screening tend to have a better prognosis than the average of all the cases

Length bias

A new blood test has been developed to screen for disease Z. Researchers establish 50 units as a cut point above which a test is considered positive and thereby indicative of disease. The test manufacturers determine that the test's sensitivity is unacceptably low. However, the manufacturers are not concerned with the specificity and do not want the cost of the test to rise. How can they improve the sensitivity of the test?

Lower the cut point below 50 units

Dr. Poke and Jab (2014) conducted an employee health program that used 5 screening tests at the same time to detect diseases among workers. Which type of program is this?

Multiphasic screening

An attributable-risk percent of 85% was calculated for the association between smoking and lung cancer death

Of those dying of lung cancer who smoke, 85% of those deaths are attributed to their smoking, assuming a casual association exists

Screening identifies an illness that would not have shown clinical signs before death from other causes

Overdiagnosis bias

Which measure is conditions on having a positive test?

Predictive value positive

Which of the following best defines specificity?

Proportion of people without the disease who have a negative test

Which of the following is the leading source of radiation?

Radon

It has been suggested that occupational exposure to benzene in the petroleum industry increases the risk of developing leukemia. The levels of benzene to which workers in this industry have been exposed were high from 1940 to 1970, but since 1970 have been significantly reduced. What kind of study design, using petroleum workers, would provide the most useful information on whether benzene affects incidence rates of leukemia in this industry? You may assume that records of individual worker assignments to jobs involving benzene exposure have been maintained by the industry.

Retrospective cohort

Screening for disease involves which type of prevention?

Secondary

The screening test looks better than it actually is, because younger, healthier people are more likely to get the test

Selection bias

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

Threshold

The lowest dose at which a particular response may occur

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 than among blood donors

Latency

The time period between initial exposure and a measurable response

True or False: 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

A sentinel health event refers to

a case of unnecessary workplace disease that serves as a warning signal

Asbestos exposure has been associated with:

asbestosis, malignant mesothelioma, and lung cancer

A person with an inapparent infection:

can transmit the infection to others

Exposure to electric and magnetic fields has been linked to

childhood leukemia risk

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

diagnostic test

The Centers for Disease Control and Prevention published an article concerning the high rate of foot fungal disease in New Orleans. The article explains that there has been a high rate of foot fungal disease in New Orleans for decades. Foot fungal disease in New Orleans is best described as:

endemic

One must use care in interpreting occupational differences in morbidity and mortality because:

good health status may be a factor for selection into a job.

Someone suggests immunization as a means of reducing disease, specifically the feared UJ (uderlinger jacamoodi). What part of the disease cycle is he or she trying to affect?

host

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

The degree of agreement among several trained experts refers to

inter-judge reliability

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

A double-blind study of a vaccine is one in which:

neither observers nor subjects know which subject receives the vaccine and which receives a placebo

The sit where a disease agent enters the body is the:

portal of entry

The public health officer from Long Beach complains to you about the dreaded Pacific Pox. The health officer says, "If people catch the Pox, they suddenly get the urge to dance in the sand and fall dead on the beach within the hour." There are no survivers to interview so you deduce:

the case fatality rate of the Pox must be high

With respect to a hypothetical rabies investigation conducted among veterinary workers (Dr. Spot, 2003), researchers found that rabies was almost always fatal. This finding refers to:

virulence