HSC 404 Final Exam

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

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

A new screening test for lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of lyme disease among clinic attendees is 10%. The predictive value of a positive test is:

18.2%

An outbreak of salmonellosis occurred after an epidemiology department luncheon, which was attended by 485 faculty and staff. Assume everyone ate the same food items. Sixty-five people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attend the luncheon revealed an additional 72 cases. The attack rate of salmonellosis was:

28.2%

An outbreak of salmonellosis occurred after an epidemiology department luncheon, which was attended by 485 faculty and staff. Assume everyone ate the same food items. Sixty-five people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attend the luncheon revealed an additional 72 cases. The virulence of salmonellosis was:

47.4%

An outbreak of salmonellosis occurred after an epidemiology department luncheon, which was attended by 485 faculty and staff. Assume everyone ate the same food items. Sixty-five people had fever and diarrhea, five of these people were severely affected. Subsequent laboratory tests on everyone who attend the luncheon revealed an additional 72 cases. The ratio of severe cases to other clinically apparent cases was:

5/60

A new screening test for lyme disease is developed for use in the general population. The sensitivity and specificity of the new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of lyme disease among clinic attendees is 10%. The number of false positives is:

81

A sentinel health event refers to:

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

Synergism:

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

What factor(s) compromise the epidemiologic triangle?

Agent, host, and environment

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

Asbestos exposure has been associated with:

Asbestosis, malignant mesothelioma, and lung cancer

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

Attributable risk

Several studies have found that approximately 85% of cases of lung cancer are due to cigarette smoking. This measure is an example of:

Attributable risk

The purpose of a double-blind study is to:

Avoid observer and interviewee bias

In a case-control study of the relationship of radiation exposure and thyroid cancer, 50 cases admitted for thyroid cancer and 100 "controls" admitted during the same period for treatment of hernias were studied. Only the cases were interviewed, and 20 of the cases were found to have been exposed to x-ray therapy in the past, based on the interviews and medical records. The controls were not interviewed, but a review of their hospital records when they were admitted for hernia surgery revealed that only 2 controls had been exposed to x-ray therapy in the past. Based on the description, what source of bias is least likely to be present in this study?

Bias due to loss of subjects from control groups over time

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

Blinding

A person with an inapparent infection:

Can transmit the infection to others

Recall bias is most likely to occur in:

Case control studies

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 CDC 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

The healthy worker effect:

Healthy persons are more likely to gain employment than unhealthy persons

Someone suggests immunization as a means of reducing disease, specifically the feared UJ (underlinger 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

Which of the following is not a type of selection bias in cohort studies:

Interviewer bias

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 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

Drs 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

When assessing a positive relationship between alcohol consumption and oral cancer using a case-control study, increasing the sample size of the study will result in which of the following? I. A lower p value II. A greeted odds ratio III. A smaller 95% confidence interval IV. A higher disease prevalence

None of the above

An attributable-risk percent of 80% was calculated for the association between smoking and lung cancer death. Which of the following provides the best interpretation of this statistic?

Of those dying of lung cancer who smoke, 80% of those deaths are attributed to their smoking, assuming a causal association exists.

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

Portal of entry

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

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

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

Standardized protocol for structured interviews

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 survivors to interview so you deduce:

The case fatality rate of the Pox must be high

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.

The population etiologic fraction is a measure of the proportion of the disease rate in a population attributable to the exposure of interest. The measure of effect is influence by:

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

Latency:

The time period between initial exposure and a measurable response

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