Key Terms for Exam 2

Question 1

agent

Answer 1

causative factor invading a susceptible host through an environment favorable to produce disease, such as a biological or chemical agent.

Question 2

analytic epidemiology

Answer 2

a form of epidemiology that investigates causes and associations between factors or events and health.

Question 3

attack rate

Answer 3

a type of incidence rate defined as the proportion of persons who are exposed to an agent and who develop the disease, usually for a limited time in a specific population.

Question 4

bias

Answer 4

in determining causality, a systematic error because of the way the study is designed, how it was carried out, or some unplanned events that occurred and affected the study.

Question 5

case-control study

Answer 5

an epidemiologic study design in which subjects with a specified disease or condition (cases) and a comparable group without the condition (controls) are enrolled and assessed for the presence or history of an exposure or characteristic.

Question 6

case fatality rate

Answer 6

the proportion of persons diagnosed with a specific disorder who die within a specified time.

Question 7

causal inference

Answer 7

using epidemiologic, clinical, statistical, and other scientific evidence to judge if a causal association exists between two or more factors or events. Guidelines for evaluation of evidence are often used in making causal inference. Different levels of evidence may be required for different settings, for example, clinical decisions versus policy determinations.

Question 8

cohort study

Answer 8

an epidemiologic study design in which subjects without an outcome of interest are classified according to past or present (or future) exposures or characteristics and followed over time to observe and compare the rates of some health outcome in the various exposure groups.

Question 9

confounding

Answer 9

a bias that results from the relationship between both the outcome and study factor (exposure or characteristic) and some third factor not accounted for in analysis.

Question 10

cross-sectional study

Answer 10

an epidemiologic study in which health outcomes and exposures or characteristics of interest are simultaneously ascertained and examined for an association in a population or sample, providing a picture of existing levels of all factors.

Question 11

descriptive epidemiology

Answer 11

a form of epidemiology that describes a disease according to dimensions of person, place, and time.

Question 12

determinants

Answer 12

factors that influence the risk for or distribution of health outcomes.
An influencing or determining element or factor

Question 13

distribution

Answer 13

a pattern of a health outcome in a population; the frequencies of the outcome according to various personal characteristics, geographic regions, and time.

Question 14

ecological model

Answer 14

a multidimensional model of determinants of health and disease that spans many levels from individual genetic and physiologic characteristics to broader contextual influences (e.g., neighborhood characteristics and social context). This model encompasses a broader spectrum of systems and etiologic factors than the web of causality model and includes a lifespan perspective.

Question 15

environment

Answer 15

for public health refers to all factors that constitute the context in which persons or animals live and that influence and are influenced by the host and agent–host interactions.

Question 16

epidemic

Answer 16

a rate of disease clearly in excess of the usual or expected frequency in that population.

Question 17

epidemiology

Answer 17

the study of the distribution and factors that determine health-related states or events in a population and the use of this information to control health problems.

Question 18

host

Answer 18

a human or animal that provides adequate living conditions for any given infectious agent.

Question 19

incidence proportion

Answer 19

the proportion of the population at risk who experience the event over some period of time.

Question 20

incidence rate

Answer 20

the frequency or rate of new cases of an outcome in a population; it provides an estimate of the risk of disease in that population over the period of observation.

Question 21

levels of prevention

Answer 21

a three-level model of interventions based on the stages of disease, designed to halt or reverse the process of pathological change as early as possible, thereby preventing damage.

Question 22

natural history of disease

Answer 22

the course or progression of a disease process from onset to resolution.

Question 23

negative predictive value

Answer 23

the proportion of persons with a negative test who are disease free.

Question 24

point epidemic

Answer 24

a concentration in space and time of a disease event, such that a graph of the frequency of cases over time shows a sharp point, usually suggestive of a common exposure.

Question 25

positive predictive value

Answer 25

the proportion of persons with a positive screening or diagnostic test who do have the disease (the proportion of “true positives” among all who test positive).

Question 26

prevalence proportion

Answer 26

a measure of existing disease in a population at a given time.

Question 27

primary prevention

Answer 27

a type of intervention that seeks to promote health and prevent disease from the beginning.

Question 28

proportion

Answer 28

a type of ratio in which the denominator includes the numerator.

Question 29

proportionate mortality ratio

Answer 29

the proportion of all deaths due to a specific cause.

Question 30

rate

Answer 30

a measure of the frequency of a health event in a defined population during a specified period.

Question 31

reliability

Answer 31

the precision, stability, agreement, or replicability of a measuring instrument when repeatedly used; an indication of consistency from time to time or from person to person.

Question 32

risk

Answer 32

the probability of some event or outcome occurring within a specified period.

Question 33

screening

Answer 33

the application of a test to people who are as yet asymptomatic for the purpose of classifying them with respect to their likelihood of developing a particular disease.

Question 34

secondary prevention

Answer 34

an intervention that seeks to detect disease early in its progression (early pathogenesis) before clinical signs and symptoms become apparent in order to make an early diagnosis and begin treatment.

Question 35

secular trends

Answer 35

long-term patterns of morbidity or mortality (i.e., over years or decades).

Question 36

sensitivity

Answer 36

the extent to which a test identifies those individuals who have the condition being examined.

Question 37

specificity

Answer 37

the extent to which a test identifies those individuals who do not have the disease or condition being examined.

Question 38

surveillance

Answer 38

systematic and ongoing observation and collection of data concerning disease occurrence in order to describe phenomena and detect changes in frequency or distribution.

Question 39

tertiary prevention

Answer 39

intervention that begins once the disease is obvious; the aim is to interrupt the course of the disease, reduce the amount of disability that might occur, and begin rehabilitation.

Question 40

validity

Answer 40

the accuracy of a test or measurement; how closely it measures what it claims to measure. In a screening test, validity is assessed in terms of the probability of correctly classifying an individual with regard to the disease or outcome of interest, usually in terms of sensitivity and specificity.

Question 41

web of causality

Answer 41

complex interrelations of factors interacting with each other to influence the risk for or distribution of health outcomes.