Epidemiology Final

A priori hypotheses

"a priori" is a Latin phrase that refers to "from before." In epidemiologic research, these hypotheses are formulated before collecting and analyzing data. Hypotheses established BEFORE prior knowledge of the level of health events in a specified population.

Why might studying a sample be preferred to studying a population?

- Samples can be studied more quickly than large populations. - Studying a sample is often less expensive than studying an entire population. - Studying the entire population may be impossible. - Sample results can be more accurate than results based on populations because more time and resources can be spent on training the people who observe and collect the data for samples and on procedures that improve accuracy. - Samples of the population with specific characteristics may be more appropriate for studying a certain health-related state or event, as compared with the entire population.

sample

A subset of items that have been selected from the population.

Hypothesis

A suggested explanation for an observed phenomenon or reasoned proposal predicting a possible causal association among multiple phenomena.

Field epidemiology

Application of epidemiology under the following set of general conditions: 1. the timing of the problem is unexpected; 2. a timely response is demanded; 3. public health epidemiologists must travel to and work in the field to solve the problem; and 4. the extent of the investigation is likely to be limited because of the imperative for timely intervention and by other situational constraints on study designs or methods.

What is the most common statistic to use for investigating an outbreak?

Attack rate

Human Papillomavirus (HPV)

Cancer of the cervix, anus, vagina, vulva, penis, oropharynx

Assessment

Conduct a preliminary evaluation to determine whether an excess of the health problem exists.

A case-control study showed that a strong association exists between birth order and Down syndrome.

Confounding

Etiologic investigation

Consider criteria for establishing a cause-effect relationship

Positive likelihood ratio

How much the odds of the disease increase when a test is positive. [TP/(TP+FN)]/[FP/(FP+TN)] This measure is the proportion of TPs among cases divided by the proportion of FPs among noncases. Ranges from 1 (neutral) to infinity (very positive)

Which of the following terms best describe this statement? " The frequency of disease occurrence is extremely different under different situations or conditions."

Method of Difference

Inductive reasoning

Moving from specific observations to broader generalizations.

Why is random assignment in clinical trial an effective way to avoid confounding?

Random assignment tends to balance out the effect of potential confounding factors between intervention and control groups, assuming the sample size is sufficiently large.

Best way to avoid bias when evaluating the efficacy of screening test or treatment:

Randomized control trial. Randomization.

Screening

Used to suggest whether an individual is likely to have a disease and if he or she should undergo diagnostic testing to confirm the presence of the disease. Screening is a type of secondary prevention. Used to suggest or detect disease among individuals in a population who do not yet show signs or symptoms of the health problem. Screen detection of disease is intended to identify asymptomatic individuals with a disease as early as possible to reduce morbidity and mortality from the disease.

Type II error (beta)

When H0 is not rejected, but H0 is false. "false negative".

Type I error (alpha)

When the null hypothesis (H0) is rejected, but H0 is true. "false positive".

Hepatitis B & C virus

liver cancer

power

the power of a statistical test measures the test's ability to reject the null hypothesis when it is actually false; power is directly associated with sample size. It is equal to 1-beta.

Predictive value positive (PV+)

the probability that an individual with a positive test actually has the disease

Etiology

the science and study of the causes of diseases and their modes of operation.

a case-control study found a positive association between self-reported chest radiographs during pregnancy and breast cancer this result is most likely due to

(recall) bias

Risk factor

(related term to causal component) an inherent human characteristic, a behavior, or an environmental exposure that is associated with an increased probability of experiencing a health-related state or event. For example, physical inactivity is a risk factor for dementia.

A hospital-based case-control study identified a strong association between oral contraceptives and thromboembolism. Many doctors suspected the association and hospitalized for evaluation some women who used oral contraceptives

(selection) bias

Four processes of toxicokinetics

1. Absorption; entrance of substance into the body., cell membranes must be penetrated. 2. Distribution; movement of substance from where it enters the body to other sites of the body (e.g., liver, blood, kidney, lymph circulation, lung) 3. Biotransformation; transformation produced by the body of the substance into new chemicals (metabolites), essential to survival. 4. Excretion; ejection of the substances or metabolites from the body.

Inductive reasoning relies on:

1. Exact and correct observation. 2. Accurate and correct interpretation of the facts to understand findings and their relationship to each other and to causality. 3. Clear, accurate, and rational explanations of findings, information, and facts in reference to causality. 4. Development based on scientific approaches (using facts in the analysis and in a manner that makes sense based on rational scientific knowledge).

Why samples are studied instead of populations?

1. Samples can be evaluated more quickly than large populations. 2. Studying a sample is often less expensive than studying an entire population. 3. Studying the entire population may not be possible. 4. Sample results can be more accurate than results based on populations; for samples, more time and resources can be spent on training the people who observe and collect the data and on procedures that improve accuracy. 5. Samples of the population that reflect specific characteristics may be more appropriate for studying a certain health-related state or event than the entire population.

WHO guidelines for screening guidelines:

1. The disease or condition being screened for should be a major medical problem. 2. Acceptable treatment should be available for individuals with diseases discovered in the screening process. 3. Access to healthcare facilities and services for follow-up diagnosis and treatment for the discoverable disease should be available. 4. The disease should have a recognizable course, with identifiable early and latent stages. 5. A suitable and effective test or examination for the disease should be available. 6. The test and the testing process should be acceptable to the general population. 7. The natural history of the disease or condition should be adequately understood, including the regular phases and course of the disease, with an early period identifiable through testing. 8. Policies, procedures, and threshold levels on tests should be determined in advance to establish who should be referred for further testing, diagnostics, and possible treatment. 9. The process should be simple enough to encourage large groups of people to participate.

Health Belief Model Concepts:

1. perceived susceptibility, 2. perceived severity, 3. perceived benefits, 4. perceived barriers, 5. cues to action, 6. self-efficacy

Two approaches used in survival analysis

1. survival time 2. survival rate

A "good" final report in a field investigation should include all of the following except: a. A description of the intervention and its effects. b. A review of the course of the epidemic in the form of a case study. c. A comparison of the hypotheses with the established facts. d. Tables, graphs, and charts. e. A "good" final report should include all of these things.

A

Biological plausibility

A causal association is consistent with existing medical knowledge.

Analogy

A comparison of two different things with similarities for the purpose of explanation or clarification.

Causal interference

A conclusion about the presence of a health-related state or event and the reasons for its existence.

Experimental evidence

A criterion in causal inference wherein an experimental study design has the greatest potential for supporting cause-effect relationships because of control over measurements and monitoring, the ability to establish a time sequence of events, and the ability to control for bias by employing an appropriate sample, random assignment, and blinding.

Coherence

A criterion in causal inference wherein there is consistency with known epidemiologic patterns of disease.

chance

A factor to consider when establishing the validity of a statistical association. It may explain a relationship between an exposure and disease outcome when the measured association is based on a sample of the population of interest. If everyone in the population is considered, it does not play a role. An association may appear to exist merely because of the luck of the draw—chance. As the sample size increases, the sample becomes more like the population, and the role of chance decreases. The degree to which such variability occurs may be monitored by the p value.

receiver operating characteristic (ROC) curve

A graphical plot that shows the diagnostic ability of a binary classifier for different cut points; a graphical plot of the true positive rate against the false positive rate for different discrimination thresholds. Sensitivity on the y-axis. 1-specificity on the x-axis. The ideal cutoff will give the greatest sensitivity with the highest specificity; this is the point lying closest to the top left corner of the graph (100% sensitivity and specificity)

Prior probability

A probability considered before some evidence is observed or taken into account. Probability of having a disease prior to the diagnostic test. Influenced by factors such as age, gender, and clinical characteristics.

Confidence interval

A range of values within a population parameter lies, based on random sample from the population. Can be calculated for any statistical measure from a sample. Can be used to evaluate the statistical significance of association between exposure and outcome.

Define and compare the difference between statistical inference and causal inference.

A statistical inference is an inference or conclusion made about a population based on sampled data. Causal inference is a conclusion about the presence of a health related state or event and the reason for its existence. The connection between human health and physical, chemical, biological, social, and psychosocial factors in the environment is based on causal inference. Causal inferences provide a scientific basis for medical and public health action.

Biotransformation

A substance is changed from one chemical to another (transformed) by a chemical reaction within the body. Detoxification occurs when biotransformation metabolizes a substance to lower toxicity.

Match the following methods for minimizing chance, bias, and confounding in an experimental study.

A. Increase sample size - chance B. Blinding - Bias C. Randomization - Confounding

A component cause is also called which of the following? a. Risk factor b. Web of causation c. Epidemiologic triangle d. All of the above are component causes.

A. Risk factor

Human T-cell lymphotrophic virus

Adult T-cell leukemia

Cluster

An aggregation of cases of a disease or other health-related condition, particularly cancer and birth defects, that are closely grouped in time and place.

Common-source epidemic

An epidemic that arises from a specific source. Starting at a specific point through intermittent or continuous exposure to a source over days, weeks, or years.

Random error

An incorrect result because of chance; sources of variation that are equally likely to incorrectly alter the results in one direction or the other.

Biologic gradient

An increasing risk of disease occurs with greater exposure.

Statistical inference

An interference or conclusion made about a population based on sample data.

What information should be combined with disease frequency data?

At-risk population from which the cases derived to calculate attack rates.

Epstein-Barr virus

Burkitt's lymphoma

Webs of causation play a more useful role when one is trying to describe disease etiology for which type of disease? A. Acute B. Infectious C. Chronic D. Two of the above

C. Chronic

Attack rate

Calculated by dividing the number of cases by the number of people followed. It involves a specific population during a limited time period, such as during a disease outbreak. It is also referred to as a cumulative incidence rate or risk

A randomized clinical trial found that drug A versus Placebo did not significantly improve 10-year survival (RR=0.35; 95 % confidence interval, 0.14-55.01).

Chance

Why are primary prevention measures more complex for chronic diseases such as heart disease or cancer than infectious acute conditions like cholera or lyme disease?

Chronic diseases tend to have long latency periods and multifactorial etiology. On the other hand, infectious acute conditions tend to have a single causal pathogen.

List things that should be done in preparing for fieldwork:

Conduct a literature review to better understand public health problem; communicate with experts; organize the appropriate investigation team; identify the specific roles of team members; make travel and financial arrangements; contact appropriate people in the field before departure.

Major feasibility study

Consider the resource requirements of the study. Determine the required case and control data needed, which should include laboratory and physical measurements.

Compare a direct causal association with an indirect causal association. Use specific examples.

Direct causal association involves a causal pathway with no intervening factors (e.g., an automobile accident and paralysis). Indirect causal association involves a causal pathway with intervening factors (e.g., poor diet resulting in high cholesterol, and high cholesterol resulting in arteriosclerosis).

Study test where the area under the curve is greater than 0.5

Discriminate

This factor facilitates the manifestation of a disease (e.g., housing).

Enabling factors

Enabling factors

Factors or conditions that allow or assist the health-related state or event to begin and run its course. These factors include services, living conditions, programs, societal support, skills, and resources that facilitate a health outcome's occurrence.

Reinforcing factors

Factors that support the production and transmission of disease or conditions, or that support and improve a population's health status and help control disease and conditions. The factors that help aggravate and perpetuate disease, conditions, disability, or death are negative reinforcing factors. Negative reinforcing factors are repetitive patterns of behavior that recur, perpetuate, and support a disease that is spreading. Positive reinforcing factors are those that support, enhance, and improve the control and prevention of the causation of disease.

Negative likelihood ratio

How much the odds of the disease decrease when a test is negative. [FN/(TP+FN)]/[TN/(FP+TN)] The lower the LR- for a diagnostic test, the greater the confidence we have that a person who obtains a score in the unaffected range truly does not have the health problem. Ranges from 0 (extremely negative) to 1 (neutral)

True Negative (TN)

Indicates that a person does not have the disease when in fact he or she does not. Of course, this is the preferred situation. No disease and negative test.

False negative (FN)

Indicates that a person does not have the disease when in fact he or she does. This can cause a false sense of security and a lack of needed care and treatment. Disease and negative test.

False positive (FP)

Indicates that a person has the disease when in fact he or she does not. This can cause unnecessary stress, anxiety and treatment. No disease and positive test.

True Positive (TP)

Indicates that a person has the disease when in fact he or she does. This can lead to needed care and treatment. Disease and positive test.

Three common pathways through which people are exposed to radiation:

Inhalation Ingestion Direct (external) exposure

John Stuart Mill

Introduced three methods of hypothesis formulation in disease etiology: 1. method of difference 2. method of agreement 3. method of concomitant variation

Method of difference

Involves recognizing that if the frequency of a disease differs between two locations, it may be because a particular factor varies between those two places. For example, the vastly different levels of colon cancer between Japan and the United States suggest that differences in diet may be the explanation.

Kaposi's sarcoma-associated herpes virus

Kaposi's sarcoma

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

Length bias

Confounding

Lurking variable; an extrinsic factor that is associated with a disease outcome and, independent of that association, is also associated with the exposure. Failure to control for it can cause the measured association between exposure and outcome variables to be misleading. Randomized experiment study allows to minimize confounding among groups.

Initial response

New diagnostic procedures may explain a cluster. Ensure that a written response to the concern will be received

Study test where area under the curve is 0.5

Nondiscriminate

Outbreak

Often synonymous with epidemic; sometimes the preferred word because it may escape the sensationalism associated with the word epidemic. It also applies when the scope of the disease is limited.

Overall accuracy equation

Overall accuracy = (TP + TN)/ (TP + FP + FN + TN)

predictive value positive PV+ equation

PV+ = (sensitivity x prior probability) / ([sensitivity x prior probability] + [(1-specificity) x (prior probability)])

PV+ (prior probability not specified)

PV+ = TP/ (TP + FP)

PV- (prior probability not specified)

PV- = TN / (FN+ TN)

Predictive value negative PV- equation

PV- = sensitivity x (1-prior probability) / [sensitivity x (1- prior probability)] + [(1- specificity) x prior probability]

Chronic diseases are mainly caused by what general factors?

Physical, chemical, biological, and psychosocial environment, as well as behavioral and inherent risk factors

How would you classify an epidemic if the epidemic curve showed a rapid rise, peak, and gradual decrease?

Point-source epidemic (common-source outbreak)

Area under the curve of ROC curve:

Positively associated with the accuracy of the study test. This area equals the probability of the study test correctly classifying patients as TPs or TNs.

What are two statistical challenges in cluster investigation?

Post hoc hypotheses and boundary shrinkage.

Associated with definitive onset of disease (e.g., toxin).

Precipitating factors

Increase level of susceptibility in a host (e.g., age).

Predisposing factors

When the clinical course of an illness is relatively long (chronic diseases)

Prognosis is often measured by survival analysis

Why are rates sometimes preferred to counts?

Rates are often used instead of counts because they allow comparison of the level of disease or another health event in two different populations

Fishbone diagram

Referred to a cause-effect diagram that provides a visual display of all possible causes that could potentially contribute to the disease, disorder, or condition under study.

This type of factor aggravates the presence of disease (e.g., repeated exposure).

Reinforcing Factors

Factors that influence the toxicity of a substance that enters the body:

Route of exposure; Duration of exposure; Rate an amount absorbed; Distribution and concentration within the body; Efficiency by which the body changes the substance and the metabolites produced; Ability of the substance or metabolites to pass through cell membranes and affect cell components; Duration and amount of substance or metabolites in body tissues; and Rate, amount, and site of departure of the substance or metabolites from the body.

Outcomes research

Seeks to understand the end results of clinical practices and interventions. Combining information about the care people are getting in terms of screening and diagnosis, prognosis, and treatment with the outcomes they experience, outcomes research has become important in developing better ways to monitor and improve clinical care.

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

Selection bias

Sensitivity

Sensitivity = TP / (TP + FN)

9 criteria that could be used to determine whether statistical associations were causal associations

Sir Austin Bradford Hill

Developed 6 criteria that may serve as a useful guide for establishing causality

Sir Austin Bradford Hill

Health effects of lead exposure

Some of the adverse health effects associated with lead exposure include: damaged organs including kidneys, liver, heart, brain and nerves, and other organs. Lead exposure may also result in osteoporosis, seizures, mental retardation, behavioral disorders, memory problems, and mood changes.

Specificity (screening test)

Specificity = TN / (TN + FP)

Specificity

Specificity of association means an exposure is associated with only one disease, or the disease is associated with only one exposure.

Four-stages of cluster investigation :

Stage 1. initial contact and response; collect relevant information from those reporting the possible cluster Stage 2. assessment; determine whether an excess of the health problem has occurred, confirm cases, and describe the epidemiological characteristics of the cases Stage 3. major feasibility; asses exposure and formulate a plausible hypothesis Stage 4. etiologic investigation; consider causal mechanism

In which stage of the four-stage process of a cluster investigation are attack rates calculated?

Stage II

What were the six criteria that Sir Austin Bradford Hill develop?

Strength of association,Consistency of association, Specificity Temporal relationship, Biological gradient, Biological plausibility and Experimental evidence

selection bias

Systematic error that occurs from the way participants are selected or retained in a study (Berkson's bias in case-control studies, loss to follow-up in cohort studies). Caused by choosing non-random, non representative data for analysis. May make a test look better or worse than it is really in terms of survival. For instance, a test would look better than actually if younger, healthier people are more likely to get the test.

Which of the following causal criteria are described in the following statement? "In order for an exposure to cause a disease, the exposure must precede the disease."

Temporality

Everyone eventually dies; thus, why isn't the case-fatality rate for a given disease 100%?

The case-fatality rate should be measured over a fixed, specified time period. Historically, this measure has been used with acute infectious illnesses that progress toward recovery or death over a short time period; that is, this is an appropriate measure of the deaths that result if they occur within a short time period from disease onset, and the deaths are a result of the disease.

what is the primary purpose of providing a final report in a field investigation?

The final report presents a narrative of the entire investigation process along with a review of the course of the studied epidemic as a case study.

Post hoc hypothesis

The formulation of hypotheses AFTER observation of an event such as an excess of cancer.

Epidemic

The occurrence of a disease within a specific community or region that is clearly in excess of the expected level for a given time period.

Case-fatality rate (epidemiologic measure of prognosis)

The proportion of people with a given disease who die from the disease within a specified time period. This measure is an indicator of the seriousness of the disease and the prognosis for those with the disease. Most useful for measuring prognoses of acute infectious diseases and conditions. Limitation: problem in using this measure with chronic diseases is that it is difficult to associate the death with diagnosis.

Prognosis

The prospect of recovery as anticipated from the usual course of disease; a prediction of the probable course and outcome of disease. Anticipation from the usual natural history of the disease.

Food poisoning

The result of preformed toxins that are present in foods before consumption; these toxins are often the waste products of bacteria. The two most common forms are Staphylococcus infection and botulism.

Survival time

The specific amount of time over which people survive a disease. Average or median survival time for a group of patients. Good idea of how long patients tend to live after diagnosis with disease.

Toxicokinetics

The study of how a substance enters the body and the course it takes while in the body; what the body does with a substance.

Temporality

The time sequence of events that provides insight into causal processes.

Latency period

The time when the disease is present but not symptomatic or detected. The term is sometimes used instead of incubation period for chronic diseases such as cancer.

A web of causation is more easily constructed for an infectious disease than a non-infectious chronic disease.

True

Mixed epidemic

When victims of a common-source epidemic have person-to-person contact with others and spread the disease, further propagating the health problem. Combination of common-source and propagated epidemic. Typically begin with common source and then are propagated from person to person.

Helicobacter pylori

a bacterium that can cause chronic conditions such as dyspepsia (heartburn, bloating, and nausea), gastritis (stomach inflammation), and ulcers in the stomach and duodenum, as well as stomach cancer and lymphoma. Caused by swallowing the bacteria in food or liquid or through contaminated utensils. Stomach cancer.

Health Belief Model

a conceptual framework that describes a person's health behavior as an expression of health beliefs. Understanding health behavior, behavior change requires a rational decision-making process that considers perceived susceptibility to illness, perceived consequences or seriousness of the illness, belief that recommended action is appropriate or efficacious to reduce risk, and belief that the benefits of action outweigh the costs.

Strength of association

a factor considered in causal inference. A strong statistical association between an exposure and health outcome provides greater evidence of there being a causal association because it is more likely to be real (valid).

p value

a function of sample data (a statistic) that helps determine the statistical significance of a result. It is a probability based on the condition that the null hypothesis is true; it measures the strength of evidence against the null hypothesis.

Epidemic curve

a histogram that shows the course of an epidemic by plotting the number of cases by time of onset. From the epidemic curve information, the nature of the course of the disease is determined, and the researcher can ascertain whether people were exposed and infected at about the same time or at different times; look for clustering of disease by both time and place; determine and fix the time of the index case and the time of onset of the outbreak; and use the information from incubation periods to determine time factors in the course of the disease peaks and valleys in the epidemic curve.

Overall accuracy

a measure of a screening test's validity, calculated as (TP + TN)/(TP+FN + FP+TN).

Food infection

a result of the ingestion of disease-causing organisms (pathogens) such as bacteria and microscopic plants and animals.

Method of Agreement

a single factor is common to a number of circumstances in which the disease occurs at a high frequency.

Behavior Risk Factor Surveillance System

a state-level prevalence survey in the United States that monitors actual behavioral risks, rather than information on attitudes or knowledge, associated with premature morbidity and mortality.

Risk factor

a variable associated with an increased probability of experiencing an adverse health outcome. Risk factors include certain behaviors, environmental exposures, or inherent human characteristics that increase the chance of a specific health condition.

Negative likelihood ratio (LR -)

a. (1- sensitivity) / specificity b. FN/ (TP +FN) / TN(FP + TN)

Positive likelihood ratio (LR+) equation

a. sensitivity / (1- specificity) b. TP/ (TP + FN) / FP/(FP + TN)

At-risk behavior

an activity performed by a person that puts him or her at greater risk of developing a health-related state or event.

Chronic Disease Epidemiology

an area of study that focuses on the frequency, pattern, causes, natural history, and treatment outcomes of chronic health problems (e.g., cancer, diabetes, cardiovascular disease, obesity, gastrointestinal disease)

Propagated epidemic

an epidemic that arises from an infection transmitted from one infected person to another. Spreads gradually from person to person, or result of a common source exposure that is then spread secondarily from person to person.

Systematic error

an incorrect result because of bias or a source of variation distort that alters the results in one direction. Recall bias in a case-control study is an example, where the cases or controls tend to misclassify their exposure status at different levels.

Disease cluster

an unusual aggregation, real or perceived, of health events that are grouped together in time and space and that are reported to a health agency. It generally occurs in response to the sudden introduction into the human environment of a physical stress, chemical or biological agent, or psychosocial condition.

A chronic disease may be which of the following: a. Infectious, communicable b. Noninfectious, noncommunicable c. Neither (a) nor (b) d. Both (a) and (b)

b. Noninfectious, noncommunicable

a cohort study found no statistical association between smoking and pancreatic cancer this result is most likely due to

chance

Prognostic indicator

clinical and laboratory information that help forecast the likely outcome of a disease

Lead time

difference in time between the date of diagnosis with screening and the date of diagnosis without screening

Each of the following tend to characterize an epidemiology field investigation except: a. The problem is unexpected. b. A timely response may be demanded. c. The epidemiologist's presence in the field is required to solve the problem. d. When there are several confirmed cases, it may be sufficient to identify other people as cases if they display the same signs and symptoms. e. All of the above are true.

e.

Clinical epidemiology

focuses specifically on patients and the application of epidemiologic methods to assess the efficacy of screening, diagnosis, and treatment in clinical settings. Primary aim is to identify the health consequences of employing a test or administering a treatment.

Chemical poisoning

food-borne illness that results from chemical contamination of food or drink. Chemical agents that preserve food, improve eating quality (nitrite, monosodium glutamate), or ensure a clean and sanitary food handling environment (pesticides, cleaners) can likewise cause food-borne illness if consumed in large enough amounts.

Koch's postulates

four criteria formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890 to establish a causal relationship between a causative microbe and a disease.

Web of causation

graphic, pictorial, or paradigm representation of complex sets of events or conditions caused by an array of activities connected to a common core or common experience or event.

Direct causal association

has no intermediate factor and is more obvious.

Outbreak

has the same definition as epidemic but is typically used when the event is confined to a more limited geographic area. Disease outbreak is a term used synonymously with epidemic and is technically more correct if the epidemic is confined to a localized area.

Most frequently mentioned chronic conditions:

high blood pressure, high cholesterol, and ischemic heart disease.

Ionizing radiation

high-energy radiation capable of producing ionization in substances in which it passes; radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized.

What is the primary distinction between a cluster and a sentinel health-related state or event?

in both cases the health-related state or event is unexpected however in a sentinel event, there is a known cause

Selective screening

involves applying the screening tests to high risk groups

Indirect causal association

involves one or more intervening factors and is often much more complicated and difficult to understand than a direct causal association.

Multifactorial etiology

involves the study of disease arising from many factors.

Decision tree

is a flow chart that visually presents a process through which lines and symbols lead to proper decisions and understanding of the role of certain risk factors in webs of causation.

Difference in the 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

Higher prevalence of a disease

more likely a positive test will represent TP

Lower prevalence of disease

more likely positive test will represent FP

Sentinel events

occurrences of unexpected health-related states or events that result from specific, recognized causes; the adverse health outcome has a known cause.

overdiagnosis bias

occurs when screening identifies an illness that would not have shown clinical signs before a person's death from other causes. Tends to make screening efforts look good because of increased identification of abnormalities. If abnormalities are harmless, individual may undergo unnecessary treatment, accompanying risk.

Physical stresses

of or relating to the body, such as excessive heat, cold, and noise; radiation (electromagnetic, ultrasound, microwave, x-irradiation); vehicular collisions; workplace injuries; climate change; ozone depletion; housing; and so on.

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

over-diagnosis bias

Environment

physical, biological, chemical, social, cultural, and other factors, any or all of which can influence the health status of populations. reflects the aggregate of those external conditions and influences that affect the life and development of an organism; it is all that is external to the human host.

Predictive value negative (PV-)

probability that an individual with a negative test does not have the disease

Survival rate

proportion of persons in a study or treatment group surviving for a given time after diagnosis. Measure of survival of a patient group for a specific period after diagnosis or treatment. Proportion (or %) of patients surviving a specific amount of time after diagnosis or treatment.

Cluster investigation

reviewing unusual numbers of health-related states or events, real or perceived, grouped together in time and location. Cluster investigations are conducted to confirm reported disease cases, to identify whether the number of cases is above what is expected, and, if possible, to identify causal relationships.

Length bias

screening is more likely to detect slower growing tumors that are less lethal; identifying disease that is less deadly or likely to be detected prior to death from other causes can result in making a screening program appear better than it really is. Slow progressing case of disease with better prognosis are more likely to be identified than faster-progress cases of disease with poorer prognosis.

Food-borne illnesses

sickness arising from consumption of contaminated or spoiled foodstuffs and liquids.

Yield of a screening test

the amount of screening the test can accomplish in a time period; how much disease it can detect in the screening process

Boundary shrinkage

the boundary where a possible disease cluster exists is ill defined, accentuating the apparent risk by focusing the investigation tightly on the cases that make up the cluster.

Bias

the deviation of the results from the truth; it can explain an observed association between exposure and outcome variables that is not real. See also systematic error. Bias is minimized by properly designing and conducting the research investigation.

Precipitating factors

the factors essential for the development of diseases, conditions, injuries, disability, and death. An example of a precipitating factor is an infectious agent that is associated with the definitive onset of the disease. Lack of seat belt use in the car, drinking and driving, and lack of helmet use by motorcycle riders all precipitate a higher level of traffic deaths.

method of concomitant variation

the frequency or strength of a risk factor varies in proportion to the frequency of the disease or condition.

Posterior probability

the name sometimes given to predictive value positive and predictive value negative probabilities because they are determined after the test results

sensitivity of a screening test

the proportion of positive tests among those who actually have the disease [TP/(TP+FN)]

Specificity of screening test

the proportion of subjects with a negative test result who do not actually have the disease. [TN/(FP+TN)]

Validity

the quality of being consistent with the truth; reflects the component of accuracy in a study concerned with the level of systematic error. Validity of a test is shown by how well the test actually measures what it is supposed to measure.

Reliability

the quality of performing consistently well over time. In clinical epidemiology, it refers to consistency of a test over time—its repeatability.

Consistency of association

the relationship between an exposure and outcome variable is replicated by different investigators in different settings with different methods.

Lead time bias

the survival time is improved because screening led to the discovery of the disease earlier, not because the time of death was extended.

Mass screening

this type of screening is not selective, but involves application of screening tests to the total population.

Predisposing factors

those existing factors or conditions that produce a susceptibility or disposition in a host to a disease or condition without actually causing it. They precede the direct cause.

Decision trees are supportive of chronic diseases and behaviorally caused diseases

true