chapter 1-7 questions Flashcards by Quynh Nga Vo

Epidemiology is broadly defines as the study of factors that influence the health of populations. The application of epidemiologic findings to decisions in the care of individual patients is:
a. Generally inappropriate
b. Known as clinical epidemiology
c. Limited to chronic disease epidemiology
d. Limited to infectious disease epidemiology
e. Limited to biologic mechanisms rather than social and environmental considerations

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Tim has a severe heart attack at age 58. The near-death experience so scares Tim that he quits smoking. Tim’s wife is also scared into quitting smoking even though she feels fine. Tim’s son resolves never to start smoking, seeing what cigarettes have done to his dad. The act of not smoking for Tim, Tim’s wife, and Tim’s son represent:

a. Host, vector, and agent effects, respectively
b. Herd immunity
c. Tertiary prevention for Tim’s son
d. Tertiary prevention, primary prevention, and secondary prevention, respectively
e. Tertiary prevention, secondary prevention, and primary prevention, respectively

i. Tertiary prevention – prevents further progression of disease based on appearance of symptoms
ii. Secondary prevention – stop risk factor behavior to prevent progression of asymptomatic disease
iii. Primary prevention – earliest possible prevention – not smoking in the first place

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Before quitting smoking, Tim, his cigarettes, and his tobacco smoke represent:

a. Agent, host, and environment, respectively
b. Agent, environment, and vector, respectively
c. Vector, agent, and vehicle, respectively
d. Host, vehicle, and agent, respectively
e. Vehicle, vector and agent respectively

i. A vehicle is an inanimate carrier of an agent of harm
ii. A host is a susceptible individual
iii. A vector and an unaffected carrier
iv. An agent is the medium of harm

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For an infectious disease to occur, there must be interactions between:

a. Behavioral factors and genetic factors
b. The agent and the vector
c. The host and the agent
d. The vector and the environment
e. The vector and the host

i. Also requires the environment for them to come together
ii. A vector may or may not be involved

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An example of the iceberg phenomenon would be:

a. The primary prevention of colon cancer
b. Giving a medicine that only partially treats an illness
c. Widely publicized fatalities caused by emerging swine flu
d. Conducting field trials in northern latitudes
e. When cold temperatures favor disease outbreaks

The first few cases of an emerging disease are typically the worst. These patients are considered the tip of the iceberg. The less severe patients are hidden from view initially and are considered the rest of the iceberg.

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Which of the following is beyond the scope of activities undertaken by epidemiologists?

a. Analyzing cost effectiveness
b. Establishing modes of disease transmission
c. Studying how to prevent disease
d. Providing data for genetic counseling
e. Rationing health care resources

This is a political task that epidemiologists don’t need to worry about

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Herd immunity refers to:

a. Immunity acquired from vaccines developed in herd animals
b. Immunity naturally acquired within confined herds of animals or within overcrowded human populations
c. The high levels of antibody present in a population after an epidemic
d. The prevention of disease transmission to susceptible individuals through acquired immunity in others
e. The vaccination of domestic animals to prevent disease transmission to humans.

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Attempts to eradicate a disease through widespread immunization programs may be associated with potential adverse effects. Which of the following adverse effects is correlated with the effectiveness of a vaccine?

a. The emergence of resistant strains of infectious agents to which the vaccine is targeted
b. The loss of the natural booster effect
c. The occurrence of infection in younger age groups
d. The occurrence of allergic reactions
e. The risk of disorders of the autism spectrum

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An airline implements a new policy requiring children over 1 year of age to have their own seats and seat belts (rather than being allowed to sit in a parent’s lab). Public health advocates support the policy because the goal is to improve travel safety. Unfortunately, given the expense of an additional plane ticket, many families choose to drive rather than fly to destinations after passage of the policy. Because road travel is substantially more dangerous than air travel, the new policy actually results in a decrease in travel safety. From a public health perspective, the results of this policy are example of:

a. Antigenic shift
b. Demographic gap
c. Ecological perspective
d. Clinical epidemiology
e. Unintended consequences

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Evaluation of which of the following potentially preventable causes of disease is most likely to raise ethical concerns?

a. Dietary intake
b. Genetic susceptibility
c. Immunization status
d. Smoking status
e. Social support networks

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While the pork industry lobbied aggressively against dubbing the novel H1N1 influenza virus swine flu, substantial evidence supported that this wholly new genetic variant of influenza developed from confined animal feed operations associated with commercial pig farming. The novel H1N1 virus resulted from:

a. Antigenic shift
b. Antigenic drift
c. Antibody shift
d. Antibody drift
e. Antisocial rift

Antigenic shift - A major genetic change
Antigenic drift - Minor alteration in surface antigens resulting from mutations
Antibody shift - Not defined phenomenon
Antibody drift - Not defined phenomenon
Antisocial rift - Occurs between competing researchers vying for the title of world’s leading influenza epidemiologist.

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A study involves tracking a condition that can recur in individuals over time (e.g. heartburn or dyspepsia)..Which of the following measures would allow the authors of the study to make full use of their collected data?

a. Attributable risk
b. Incidence density
c. Period prevalence
d. Point prevalence
e. Proportional hazards

Incidence density - Measure reported in terms of the frequency (density) of a condition per person-time. (person-days, person-months, etc)

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During a given year, 12 cases of disease X are detected in a population of 70,000 college students when those 12 students present for medical attention. Many more students have mild symptoms of the disease and do not seek care. Of the 12 detected cases, 7 result in death. The ratio of 7/12 represents:

a. The case fatality ratio
b. The crude death rate
c. The pathogenicity
d. The standardized mortality ratio
e. 1-prevalence

a. The case fatality ratio
b. The crude death rate
i. # of deaths caused by the condition / mid-period population
c. The pathogenicity
i. The proportion of infected persons with clinical illness
d. The standardized mortality ratio
i. The number of observed deaths based on a reference population
e. 1-prevalence
i. Not meaningful

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During a given year, 12 cases of disease X are detected in a population of 70,000 college students when those 12 students present for medical attention. Many more students have mild symptoms of the disease and do not seek care. To report the incidence rate of disease X, it would be necessary to know:

a. Nothing more than the data provided
b. The pathogenicity
c. The infectiousness of the disease
d. The duration of the clinical illness
e. The midyear population at risk

e. The midyear population at risk
i. Incidence rate = # of new cases in a specified population, during a specific period / the mid-period population at risk.

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During a given year, 12 cases of disease X are detected in a population of 70,000 college students when those 12 students present for medical attention. Many more students have mild symptoms of the disease and do not seek care. To report the prevalence of disease X, it would be necessary to know:

a. The cure rate
b. The duration of illness
c. The number of cases at a given time
d. The number of losses to follow-up
e. The rate at which new cases developed

c. The number of cases at a given time

i. Prevalence = # of cases in a specified population at a particular time.

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This is calculated after the two populations to be compared are “given” the same age distribution, which is applied to the observed age-specific death rates of each population.

a. Age-specific death rate
b. Case fatality ratio
c. Cause-specific death rate
d. Crude birth rate
e. Direct standardization of death rate
f. Incidence rate
g. Indirect standardizations of death rate
h. Infant mortality rate
i. Prevalence rate
j. Standardized mortality ratio
k. Standardized rate

e. Direct standardization of death rate

i. The age-specific death rates are available for the populations to be compared

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This is the number of new cases over a defined study period, divided by the mid-period population at risk.

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This is used if age-specific death rates are unavailable in the population whose crude death rate is to be adjusted.

g. Indirect standardizations of death rate - Applies the death rates from a reference population to the study populations.

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This is not a true rate; it is actually a proportion.

prevalence rate - the prevalence rate is not a true rate, only the proportion, or percentage, of persons in a specified population with a defined condition at the time of study.

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This is the observed total deaths in a population, divided by the expected deaths in that population, multiplied by 100.

j. Standardized mortality ratio

i. Often derived from indirect standardization methods.

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This is useful for studying trends in the causes of death over time.

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This is often used as an overall index of the health status of a country.

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This is a fictitious rate.

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This is the proportion of individuals with a given condition who die of the condition.

b. Case fatality ratio

i. Requires knowing the number of affected individuals and the number of deaths attributable to the condition.

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This is the number of live births, divided by the mid-period population. a. Age-specific death rate b. Case fatality ratio c. Cause-specific death rate d. Crude birth rate e. Direct standardization of death rate f. Incidence rate g. Indirect standardizations of death rate h. Infant mortality rate i. Prevalence rate j. Standardized mortality ratio k. Standardized rate

d. Crude birth rate i. Technically not a valid rate because not everyone in the denominator can be said to be “at risk” for the numerator event (i.e. only women of childbearing age are at risk for bearing children).

15. This provides the death rate within a defined age range. a. Age-specific death rate b. Case fatality ratio c. Cause-specific death rate d. Crude birth rate e. Direct standardization of death rate f. Incidence rate g. Indirect standardizations of death rate h. Infant mortality rate i. Prevalence rate j. Standardized mortality ratio k. Standardized rate

a Age is one of the strongest predictors of mortality. Death rate that do not reflect the experience of particular age groups are difficult to interpret. Uses the population within a particular age range as the denominator and use deaths within that group as the numerator.

An outbreak of disease should be reported to the local or state health department: a. Only if the diagnosis is certain b. Only if the disease is infectious c. Only if the disease is serious. d. Only if the outbreak involves at least 10 people e. Always.

Arizona, Colorado, and New Mexico report cases of an unexplained respiratory tract illness with a high case fatality ratio. Which of the following is most reliably true regarding this event? a. The cases represent an epidemic b. The identification of the cases is an example of active surveillance c. It is appropriate for the CDC to investigate the cases d. The seemingly new cases may be an artifact of improved health department surveillance. e. If the illnesses represent an endemic disease, the cases do not constitute an outbreak.

Cases of “flesh-eating” group A streptococcal disease are reported in a defined population. Which of the following types of information would be most helpful for determining whether these cases represent a disease outbreak? a. The clinical features and methods of diagnosing the disease b. The disease vector and reservoir c. The exact location and timing of disease onset d. The incubation period and pattern of disease transmission e. The usual disease patterns and reporting practices

An official from the state department of public health visits outpatient clinics and emergency department to determine the number of cases of post-exposure prophylaxis for rabies. The official’s action is an example of: a. Active surveillance b. Case finding c. Outbreak investigation d. Screening e. Secondary prevention

An article highlighting the long-term consequences of inadequately treated Lyme disease is published in a medical journal. After a summary of the article appears in popular newspapers and magazines, patients with vague joint pains begin insisting that their physicians test them for Lyme disease. Cases in which the test results are positive are reported as cases of Lyme borreliosis. This represents: a. Outbreak investigation b. An epidemic of Lyme borreliosis c. A change in reporting that would underestimate incidence d. A change in surveillance that would overestimate the prevalence e. A change in screening that would underestimate the likelihood of an outbreak

d. A change in surveillance that would overestimate the prevalence i. Whenever public attention is focused on a particular health problem, an increase in the number of reported cases of the problem is likely.

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. That 11 of 17 diners become sick: a. Is a coincidence until proven otherwise b. Represents a disease outbreak c. Is attributable to bacterial infection d. Is not an outbreak because the usual pattern of disease is unknown e. Should be investigated by the CDC.

e) 11/17 attack rate is the proportion of exposed persons who become ill

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. ``` The earliest priority in investigating the phenomenon would be to: A. Close the kitchen temporarily B. Define a case investigation. C. Perform a case-control study D. Perform stool tests E. Submit food samples to the laboratory ```

B) Define a case | 1. Establishing a diagnosis or a case definition is the earliest priority in an outbreak investigation.

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. The best case definition for the guests’ disease would be: A. Abdominal pain, vomiting, and diarrhea within 24 hours of the luncheon B. Acute viral gastroenteritis C. Staphylococcal food poisoning D. The onset of abdominal pain and fever after the luncheon E. An elevated white blood cell count

A. Abdominal pain, vomiting, and diarrhea within 24 hours of the luncheon 1. The case definition is required to distinguish between cases and non-cases of the disease under investigation (i.e. distinguish who is “ill” and who is “not ill” by strict criteria.)

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. Suspecting that the disease may be the result of a common-source exposure involving contaminated food, the investigators attempt to determine which food is responsible. Their initial task is to: a. Analyze food specimens from the luncheon in the laboratory b. Close the kitchen c. Examine the kitchen and interview the food preparers about their techniques d. Interview luncheon attendees to find out what they ate. e. Perform a case-control study.

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. The investigators are confident of a food source of the outbreak but are unable to identify a single food that was eaten by every symptomatic guest. They should: a. Abandon the investigation because the disease is not that serious. b. Conclude that the disease was not actually food-borne. c. Conclude the investigation without identifying a source d. Implicate all foods served at the luncheon as possible sources and purge the kitchen of all remnants. e. Implicate the food most eaten only by those with symptoms.

The U.S. President invites a group of legislators to a formal luncheon at the White House. Within 24 hours, 11 of the 17 diners experience abdominal pain, vomiting, and diarrhea. The President does not eat the salmon and feels fine. Of the 11 symptomatic guests, 4 have fever and 7 do not; 5 have an elevated white blood cell count and 6 do not; 6 ate shrimp bisque and 5 did not; 9 ate salmon mousse and 2 did not; and 1 goes on to have surgery for acute cholecystitis resulting from an impacted calculus (stone) in the common bile duct. Of the 11 symptomatic guests, 10 recover within 3 days; the exception is the senator who underwent surgery and recovered over a longer period. The guests at this luncheon had shared no other meals at any time recently. The investigators suspect that the salmon mousse is the source of the disease. To confirm or refute their suspicion, they should: a. Identify the causative agent.. b. Initiate active surveillance c. Conduct a prospective study feeding volunteers salmon mouse to see how many of them become ill. d. Perform a case-control study in which the cases are the guests who ate salmon mousse and the controls are those who did not. e. Perform a case-control study in which the cases are the guests who became ill and the controls are those who did not.

This must be associated with the exposure and the outcome. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

b. Confounder - The third variable in question is not in the causal pathway between the two. Cigarette smoking is a confounder of the relationship between alcohol consumption and lung cancer. Cigarette smoking is associated with the outcome, lung cancer, and with the exposure, alcohol consumption, but is not thought to be involved in the pathway through with alcohol could lead to lung cancer.

This alters the nature of a true relationship between an exposure and an outcome. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

c i. Unlike the confounder, an effect modifier does not obscure the nature of a relationship between two other variables; rather, it changes the relationship.

3. An example of this type of systematic distortion of study data is weighting subjects while they are fully dressed. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

g. Measurement bias | i. In contrast to random error, measurement bias is a systematic distortion of study data.

This is a multiplicative effect between exposure variables: a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

When the study sample adequately resembles the larger population from with it was drawn, the study is said to have this. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is present if it is possible to conceive of a mechanism by which an apparent cause could induce an apparent effect. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is a means or the means by which the causal factor leads to the outcome. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is absolutely required for a disease to occur, but it will not necessarily produce the disease. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is a systematic distortion in outcome assessments in retrospective studies; it is eliminated by a prospective design. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is sufficient to produce disease: a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

This is present when study results are obtained in an unbiased manner. a. Biologic plausibility b. Confounder c. Effect modifier d. External validity e. Internal validity f. Intervening variable g. Measurement bias h. Necessary cause i. Recall bias j. Sufficient cause k. Synergism

e The most important criterion on which a study is judged is its internal validity. The study must obtain its study results in an unbiased manner to be internally valid.

The basic goal of epidemiologic research is to: a. Describe associations between exposures and outcomes. b. Identify sources of measurement error and bias c. Establish direct causality d. Maximize external validity e. Reject the alternative hypothesis

Studies may be conducted to generate or test hypotheses. The best design for testing a hypothesis is a: a. Case-control study b. Cross-sectional survey c. Longitudinal ecological study d. Randomized controlled trial e. Retrospective cohort study

d Randomized controlled trials are experimental studies and represent the “gold standard” for hypothesis testing

The members of a public health team have a continuing interest in controlling measles infection through vaccination. To estimate the level of immunity in a particular population in a quick and efficient manner, what type of study should they conduct? a. Case-control study of measles infection b. Cross-sectional survey of vaccination status c. Randomized trial of measles vaccination d. Retrospective cohort study of measles vaccination e. Ecological study of measles in the population

A published study purpoted to show that a variety of symptoms were more common among participants with a history of suboptimally treated Lyme disease than among controls who had no history of Lyme disease. The data were obtained largely by a survey of the participants. The study is most likely subject to which of the following distortions? a. Ecological fallacy, length bias, and lead-time bias b. Intervention bias, random error, and length bias c. Late-look bias, measurement bias, and length bias d. Lead-time bias, late-look bias, and selection bias e. Selection bias, recall bias, and random error

Cross-sectional surveys are subject to the Neyman bias, or late-look bias. This may be explained as the tendency to: a. Detect only the late stages of a disease, when manifestations are more severe. b. Detect only the cases of a disease that are asymptomatic c. Find more disease in older cohort d. Detect fatalities preferentially e. Detect the more indolent cases of a disease preferentially.

A potential bias in screening programs that is analogous to the late-look bias is: a. Spectrum bias, because the cases are clustered at one end of the disease spectrum b. Retrospective bias, because the severity of illness can only be appreciated in retrospect c. Length bias, because cases lasting longer are more apt to be detected d. Selection bias, because the program selects out severe cases e. Selection bias, because the program selects out asymptomatic illness

In assessing the extent of a population’s exposure to an infectious agent, the measurement of IgG and IgM titers is: a. Of limited usefulness because the titers decline with time b. Useful for distinguishing cell-mediated from humoral immunity c. Useful for distinguishing remote from recent exposure d. Useful for distinguishing vaccination from infection e. Not useful

Which of the following measures the chance of having a risk factor? a. Kappa b. Odds ratio c. P value d. Relative risk e. Risk ratio

B a. Kappa i. Measure of inter-rater agreement b. Odds ratio i. Usually derived from a case-control study, indicates the relative frequency of a particular risk factor in the cases and in the controls c. P value i. Measure of statistical significance. d. Relative risk i. Same as risk ratio e. Risk ratio i. Used when the disease in question is rare. Estimated by odds ratio.

A case-control study may have a particular advantage over a cohort study when the disease in question is: a. Fatal b. Indolent c. Infectious d. Virulent e. Rare

In a case-control study that is being planned to study possible causes of myocardial infarction, patients with MI serve as the cases. Which of the following would be a good choice to serve as the controls? a. Patients whose cardiac risk factors are similar to those of the cases and who have never had an MI in the past b. Patients whose cardiac risk factors are similar to those of the cases and who have had an MI in the past. c. Patients whose cardiac risk factors are dissimilar to those of the cases and who have never had an MI in the past. d. Patients whose cardiac risk factors are dissimilar to those of the cases and who have had an MI in the past e. Patients whose cardiac risk factors are unknown and who have had an MI in the past.

A team of researchers hypothesize that watching violent, non-educational cartoons might lead to epilepsy in childhood. Children with and without epilepsy are compared on the basis of hours spent watching violent, non-educational cartoons. Which of the following statements best characterizes the assessment of data in such a study? a. Absolute and relative measures of risk can be derived. b. The difference in level of exposure to a putative risk factor is the basis for comparison. c. The risk ratio can be calculated directly. d. The temporal association between exposure and outcome can be established with certainty. e. The use of healthy controls ensures external validity.

The researchers in question 1 do not find statistically significant evidence that cartoons produce epilepsy in childhood. However, determined to show that violent, non-educational cartoons cause harm, they hypothesize that perhaps viewing this type of programming leads to attention deficits. They assemble two groups of children: those who watch violent, non-educational cartoons frequently and those who watch only other types of television programming. Which of the following is a characteristic of such a study? a. Additional risk factors cannot be assessed as the study progresses. b. Internal validity is independent of confounders. c. The two study groups are assembled on the basis of their outcome status. d. The most appropriate measure for comparing outcomes in this study would be an odds ratio. e. The temporal association between exposure and outcome is uncertain.

The risk of acquiring an infection is 300 per 1000 among the unvaccinated and 5 per 1000 among the vaccinated population. Approximately 80% of the population is exposed to the pathogen every year. Which of the following would be true? a. The absolute risk reduction is 295. b. The relative risk reduction is 5900%. c. The population attributable risk percent is 27. d. The number needed to treat is 6.2. e. The number needed to harm is 38.

b PAR% = ((Risk total – risk unexposed) / risk total) x 100

A study is conducted to determine the effects of prescription stimulant use on an individual’s willingness to bungee jump. A total of 500 individuals are assembled on the basis of bungee-jumping status: 250 are jumpers and 250 are not jumpers. Of the 250 jumpers, 150 report prescription stimulant use. Of the 250 non-jumpers, 50 report prescription stimulant use. Most of the non-jumpers take anxiolytics. Which of the following statements is true? A. Jumpers and non-jumpers should be matched for prescription stimulant use. B. The absolute and relative risks of bungee jumping with the use of prescription stimulants can be determined from this study. C. This is a cohort study. D. This study can be used to calculate an odds ratio. E. Unanticipated outcomes can be assessed in this study.

A study is conducted to determine the effects of prescription stimulant use on an individual’s willingness to bungee jump. A total of 500 individuals are assembled on the basis of bungee-jumping status: 250 are jumpers and 250 are not jumpers. Of the 250 jumpers, 150 report prescription stimulant use. Of the 250 non-jumpers, 50 report prescription stimulant use. Most of the non-jumpers take anxiolytics. What is the absolute difference in the risk of jumping between those using prescription stimulants and those not using these drugs? A. 0.4 B. 0.67 C. 67 D. 100 E. It cannot be calculated because this is a case-control study.

A study is conducted to determine the effects of prescription stimulant use on an individual’s willingness to bungee jump. A total of 500 individuals are assembled on the basis of bungee-jumping status: 250 are jumpers and 250 are not jumpers. Of the 250 jumpers, 150 report prescription stimulant use. Of the 250 non-jumpers, 50 report prescription stimulant use. Most of the non-jumpers take anxiolytics. The odds ratio calculated from this study would give the odds of: A. Jumping among stimulant users to jumping among non-stimulant users B. Jumping among stimulant users to non-jumping among non-stimulant users C. Non-jumping among stimulant users to non-stimulant use among jumpers D. Stimulant use among jumpers to stimulant use among non-jumpers E. Stimulant use among non-jumpers to non-stimulant use among jumpers

E OR = ad/bd a. a = cases with the exposure b. b = controls with the exposure c. c = cases without the exposure d. d = controls without the exposure

A study is conducted to determine the effects of prescription stimulant use on an individual’s willingness to bungee jump. A total of 500 individuals are assembled on the basis of bungee-jumping status: 250 are jumpers and 250 are not jumpers. Of the 250 jumpers, 150 report prescription stimulant use. Of the 250 non-jumpers, 50 report prescription stimulant use. Most of the non-jumpers take anxiolytics. The results of this study indicate that: A. Bungee jumping and stimulant use are associated. B. Bungee jumping and stimulant use are causally related. C. Bungee jumping influences one’s need for prescription stimulants. D. The use of prescription stimulants influences a person’s tendency to bungee jump. E. There is no association between anxiolytic use and bungee jumping.

You decide to investigate the stimulant use–bungee jumping association further. Your new study again involves a total of 500 individuals, with 250 in each group. This time, however, you assemble the groups on the basis of their past history of stimulant use, and you prospectively determine the incidence rate of bungee jumping. You exclude subjects with a prior history of jumping. Over a 5-year period, 135 of the exposed group and 38 of the unexposed group engage in jumping. The relative risk of bungee jumping among the group exposed to stimulant use is: A. 2.1 B. 3.6 C. 4.8 D. 6 E. Impossible to determine based on the study design

b Relative risk can be determined for cohort studies RR = [a/(a+b)] / [c/(c+d)]

You decide to investigate the stimulant use–bungee jumping association further. Your new study again involves a total of 500 individuals, with 250 in each group. This time, however, you assemble the groups on the basis of their past history of stimulant use, and you prospectively determine the incidence rate of bungee jumping. You exclude subjects with a prior history of jumping. Over a 5-year period, 135 of the exposed group and 38 of the unexposed group engage in jumping. ``` Among bungee jumpers, what percentage of the total risk for jumping is caused by stimulant use? A. 0% B. 3.6% C. 10% D. 36% E. 72% ```

E AR% (exposed) = (RR-1) / RR x 100 (3.6-1) / 3.6 x 100 = 72.2%

B 1. NNT = 1 / Absolute Risk Reduction associated with an intervention 2. ARR = intervention (antibiotic treatment) reduces the risk of death from 15% to 2% so ARR is 13% or 0.13. 1 / 0.13 = 7.7

E 1. NNH = 1 / absolute risk increase = 1 / 0.01 = 100 2. ARI = 1% risk of anaphylaxis (the adverse outcome) when antibiotic treatment (the intervention) is used and a 0% risk of anaphylaxis when antibiotic treatment is not used.

Assume that the risk of death in patients with untreated pneumonia is 15%, whereas the risk of death in patients with antibiotic-treated pneumonia is 2%. Assume also that the risk of anaphylaxis with antibiotic treatment is 1%, whereas the risk without treatment is essentially 0%. What would be the net result of intervention in this scenario? A. 1.0 patient saved for each patient harmed B. 7.7 patients harmed for each patient saved C. 13 patients saved for each patient harmed D. 39.4 patients harmed for each patient saved E. 100 patients saved for each patient harmed

C NNH / NNT = 100 / 7.7 = 13

You randomly assign clinical practices to charting with a new electronic medical record (intervention) or charting using paper records (control), and you test whether physicians are satisfied or not (outcome) after 3 months. Of 100 subjects assigned to each condition, you find evidence of satisfaction in 12 in the EMR group and 92 in the paper group. ``` An appropriate measure of association in this study is the: A. Incidence density B. Power C. Likelihood ratio D. Odds ratio E. Risk ratio outcome. ```

E Odds ratio --> Used in case-control studies Risk ratio--> This is a cohort study, in which subjects are assembled on the basis of exposure status and followed for outcome. The risk ratio is the outcome measure of a cohort study with a dichotomous outcome.

You randomly assign clinical practices to charting with a new electronic medical record (intervention) or charting using paper records (control), and you test whether physicians are satisfied or not (outcome) after 3 months. Of 100 subjects assigned to each condition, you find evidence of satisfaction in 12 in the EMR group and 92 in the paper group. ``` The value of risk ratio is: A. 0.08 B. 0.13 C. 1.3 D. 8.1 E. 13.1 ```

B The risk of the outcome in the exposed is divided by the risk of the outcome in the unexposed. In this study the outcome is physician satisfaction; the exposure is electronic medical record (EMR) charting; the risk of the outcome in the exposed is 12 / 100 or 0.12; and the risk of the outcome in the unexposed is 92 / 100 or 0.92. 0.12 / 0.92 yields 0.13.

This is calculated as c/(a+c): a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

f ) false-negative error rate

This is the ability of a test to detect a disease when it is present. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is type 1 error. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity

This defines normal and abnormal test results. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is the tendency of a measure to be correct on average. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is calculated as a/(a+c): a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is the ability of a test to exclude a disease when it is absent. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is a non-differential error. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. Flase-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

The closer this is to the upper left corner of an ROC curve, the better it is. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. False-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

This is differential error. a. Accuracy b. Alpha error c. Beta error d. Bias e. Cutoff point f. Flase-negative error rate g. False-positive error rate h. Positive predictive value i. Precision j. Random error k. Sensitivity l. Specificity

The likelihood ratio associated with the use of serum creatine kinase (CK) levels for the diagnosis of myocardial infarction varies with the: a. Cutoff point b. Degrees of freedom c. Posterior probability d. Value of alpha e. Value of beta

As the sensitivity increases, which of the following generally occurs? a. The cutoff point decreases. b. The false-negative error rate increases. c. The false-positive error rate increases. d. The specificity increases. e. The statistical power decreases.

Two radiologists interpret 100 mammograms. They agree that the results are normal in 70 mammograms and abnormal in 12 mammograms. In the remaining 18 cases, the first radiologist thinks that the results are normal in 6 mammograms and abnormal in 12 mammograms, wheras the second radiologist thinks just the opposite. The value of an appropriate measurement of their agreement is: a. 6% b. 16% c. 26% d. 46% e. 86%

The clinicians in a primary care clinic do not know the prevalence of Chlamydia trachomatis infection in their community. In screening patients for this infection, they plan to use a test that preformed with a sensitivity of 75% and a specificity of 75% in clinical trials. When the clinicians use the test to screen patients for C. trachomatis in their own community, which of the following could they use to help them interpret a positive test result? a. Kappa b. Phi c. LR+ d. Odds ratio e. RR

The clinicians in a primary care clinic do not know the prevalence of Chlamydia trachomatis infection in their community. In screening patient for this infection, they plan to use a test that preformed with a sensitivity of 75% and a specificity of 75% in clinical trials. What is the value for the measure specified in question 14? a. 2.6 b. 3 c. 5 d. 8.4 e. 16