Epi Flashcards
What is the Prevention Paradox?
The idea that a policy or intervention that’s good for the population as a whole may only be marginally beneficial for individuals
It is based on the observation that most cases of a disease come from people with low or moderate risk.
Define Evidence Based Medicine.
The explicit use of best available evidence for decision making at the level of the individual patient
Challenges include publication bias and time consumption.
What is Evidence Based Policy?
The use of evidence in policy decision, leading to better and more efficient outcomes.
What is a Descriptive Study?
A study designed only to describe the existing distribution of variables in a population without regard to causal or other hypotheses.
What is an Observational Study?
An epidemiologic study in which the role of the investigator is to be a mere observer of what happens.
What characterizes an Analytical Study?
A study designed to test a hypothesis, generally to examine whether a certain exposure is a risk factor for a particular disease.
What is a Case-Control Study?
An observational study that starts with the identification of a group of cases and a group of suitable controls, measuring exposure to a risk factor.
What is a Nested Case-Control Study?
A case-control study in which cases and controls are drawn from the population in a cohort study.
Define Cross-Sectional Study.
A study in which information on risk factors and outcomes are measured simultaneously at one point in time.
What is a Cohort Study?
A study in which a group of persons exposed and a group unexposed to a potential risk factor are followed up over time.
What is a Historical Cohort Study?
A cohort study that relies upon data collected in the past.
What is an Ecological Study?
An epidemiological study where the units of analysis are populations or groups of people rather than individuals.
What is a Cluster Randomised Trial?
A trial in which groups of individuals (clusters) are randomised, and all individuals within a cluster receive the same intervention.
Define Clinical Trial.
An intervention study in which the unit of allocation to different groups is the individual patient.
What is a Randomised Clinical Trial?
An experimental study in which subjects are randomly allocated to receive or not receive the intervention.
What is a Single-Blind Trial?
A trial in which either the subject or the observer measuring the outcome is unaware of the treatment the subject is receiving.
What is a Double-Blind Trial?
A trial in which neither the subject nor the observer measuring the outcomes know which treatment the subject has received.
What is a Crossover Trial?
A type of randomised clinical trial in which each subject acts as their own control by receiving at least two different treatments at different times.
What is a Factorial Trial?
A design of randomised clinical trial in which two or more interventions are compared, either alone or in combination.
What is a Field Trial?
A trial in which the subjects are members of the general population and not patients.
What is a Community Trial?
A trial in which the unit of allocation is an entire community.
What is a Hospital-Based Study?
A study in which the subjects are drawn from a list of patients in a hospital.
Define Prospective Study.
A study in which data are collected in an ongoing way during the study.
What is a Retrospective Study?
A study in which data about the study subjects were collected from past records.
What does a Study of Disease Prognosis estimate?
The frequency with which different disease outcomes can be expected to occur.
Define Absolute Risk.
A measure of association indicating how much greater the frequency of disease is in the exposed group compared with the unexposed.
What are Adjusted Measures?
Measures for which the effects of differences in the distribution of confounders have been minimized using statistical techniques.
What is the Attack Rate?
A cumulative incidence rate usually used for an infectious disease in an epidemic.
What does Attributable Risk indicate?
The risk of disease in the exposed group that can be considered attributable to the exposure.
Define Population Attributable Risk.
An estimate of the excess risk of disease in the total study population attributable to the exposure.
What is the Case-Fatality Rate?
The proportion of cases of a specified condition which are fatal within a specified period of time.
What is a Crude Rate?
A rate in the total population as a whole, without adjustment for potential confounders.
Define Incidence.
The number of new cases of disease that develop in a population of individuals at risk during a specified time interval.
What is an Odds Ratio?
A measure of relative risk comparing the odds of disease in the exposed to the odds of disease in the unexposed.
What is Person-Time?
A measurement combining number of people and time observed, used as a denominator in the calculation of rates.
Define Period Prevalence.
The total number of individuals in a population who had the disease or health event of interest at any time during a specified period.
What is person-time?
A measurement combining number of people and time observed, used as a denominator in the calculation of rates. It represents the sum of each individual’s time at risk, usually expressed as person-years.
Define period prevalence.
The total number of individuals in a population who had the disease or health event of interest at any time during a specified (short) period, taken as a proportion of the total population.
What is point prevalence?
The number of cases of disease in a population at one point in time, taken as a proportion of the total number of people in that population at the same point in time.
What does proportional mortality ratio indicate?
The proportion of observed deaths from a specified condition in a defined population divided by the proportion of deaths expected from this condition in a standard population.
What is the prevalence difference?
The absolute difference in the prevalence of disease in those exposed to a putative risk factor and those not exposed.
Define prevalence ratio.
A measure of the strength of an association; the ratio of the prevalence of the outcome of interest in those exposed to the putative risk factor to the prevalence in the unexposed.
What is a proportion?
A type of ratio in which the numerator is included in the denominator, taking values between 0 and 1.
Define rate.
A special type of ratio in which the denominator is expressed in units of person-time at risk.
What is the rate difference?
The absolute difference in incidence rate between a group of individuals exposed to a potential risk factor and a group not exposed.
What is relative risk?
Estimates the magnitude of an association between exposure and disease, indicating likelihood of disease development in those exposed relative to those unexposed.
What is standardisation?
A set of techniques used to remove the effects of differences in age or other confounding variables when comparing populations.
What is the standardized mortality ratio (SMR)?
The ratio of the number of events observed in the study group to the number expected, allowing for age, sex, and other confounders.
Define birth rate.
A summary rate based on the number of live births in a population over a given period, usually one year.
What is the infant mortality rate (IMR)?
A measure of the yearly frequency of deaths in children less than one year old per number of live births in the same year.
What does burden of disease measure?
Impact of disease in a population, accounting for number of events and severity/impact on quality of life.
What is the global burden of disease study (GBD)?
A comprehensive research program assessing mortality and disability from major diseases, injuries, and risk factors.
What is health-adjusted life expectancy?
Average number of years a person can expect to live in full health, incorporating information on mortality and health status.
Define number needed to treat (NNT).
The number of patients who need to receive a treatment for one patient to benefit with respect to the outcome of interest.
What is negative predictive value?
The proportion of people who truly do not have a disease or risk factor out of those with a negative result in a screening test.
What is mass screening?
Screening of the whole population.
Define positive predictive value.
The proportion of people who truly have a disease or risk factor out of those with a positive result in a screening test.
What does specificity measure?
The proportion of truly non-diseased persons identified correctly by the screening test.
What is the basic reproductive rate (R₀)?
The expected number of cases directly generated by one case in a fully susceptible population, indicating the transmissibility of an infectious disease.
What is herd immunity?
The immunity of a group or community based on the resistance to infection of a high proportion of individual members.
What is the epidemic threshold?
The fraction of the population that must be susceptible for an epidemic to occur.
Define attack rate.
The proportion of a group that experiences the outcome under study over a given period, used traditionally in outbreak investigations.
What is the latent period?
The time between exposure to an agent and the infectious period starting.
What is bias in study design?
Errors that cause a systematic deviation from the truth, leading to consistent differences between recorded values and true values.
What is blinding in research?
Concealing information about exposure or outcome from participants and observers to reduce bias.
What is confounding?
A situation where an estimate of the association between an exposure and a disease is distorted due to another associated factor.
What is reverse causality?
The association where the outcome causes a change in the exposure rather than the other way around.
What is confounding?
A type of bias causing an observed association where none exists or causing reverse associations.
Confounding can lead to underestimation or overestimation of associations.
What is reverse causality?
The association between an exposure and an outcome is due to the outcome causing a change in the exposure.
What criteria are used to assess true causality?
Bradford Hill criteria, after ruling out chance, bias, confounding, and reverse causality.
Define ‘control’ in intervention studies.
An individual in a comparison group who did not receive the intervention under study.
What is a ‘determinant’ in epidemiology?
Any factor that brings about a change in a health condition.
What is ecological bias?
Bias that occurs when results from an ecological study are extrapolated to individuals.
Define mediator/intermediate factor.
A variable that is on the causal pathway between an exposure and outcome of interest.
What is an effect modifier?
A factor that modifies the effect of the putative causal factor under study.
What does ‘effectiveness’ refer to?
The extent to which an intervention does what it is intended to do when applied through a routine delivery system.
What is the difference between efficacy and effectiveness?
Efficacy refers to the extent an intervention works under ideal conditions; effectiveness refers to its performance in real-world settings.
What is equipoise?
A state of genuine uncertainty about the benefits or harms that may result from different exposures or interventions.
What characterizes an epidemic?
The occurrence of an illness or health-related event sharply exceeding what is normally expected in a defined population.
Who are the ‘exposed’ in epidemiology?
Individuals who have been exposed to a putative cause of a disease or condition of interest.
Fill in the blank: The relationship in which a change in exposure is associated with a change in risk is called the _______.
exposure-response relationship.
What is genetic epidemiology?
The study of the role of genetic factors and their interaction with environmental factors in disease occurrence.
What is a genome-wide association study (GWAS)?
A study analyzing numerous genetic variants across the genome to measure differences associated with a disease.
Define generalizability.
The extent to which findings are applicable to populations other than that studied.
What is the healthy worker effect?
A type of selection bias occurring in occupational cohorts where workers have lower morbidity and mortality rates than the general population.
What is primary prevention?
Measures taken to prevent the onset of illness and injury.
What does matching refer to in epidemiological studies?
A technique used to adjust for confounding by selecting controls that match the distribution of potential confounders among cases.
What is observer bias?
A type of measurement bias where data gathering is influenced by the investigator’s knowledge of exposure or disease status.
What is a pilot study?
A small-scale study to test the feasibility of methods and procedures before a larger study.
What is a placebo?
An inert medication or procedure given to the control group in an intervention trial.
What is randomization?
The allocation of individuals to groups determined by chance.
What is recall bias?
A type of measurement bias where the ability to remember past events is influenced by disease or exposure status.
What is measurement error?
The difference between a recorded value of an exposure or outcome and the true value.
What is non-differential misclassification?
Misclassification that occurs with equal probability across study groups.
What is intention to treat analysis?
Analyzing subjects in a randomized controlled trial as originally allocated, regardless of treatment compliance.
Define differential misclassification.
Misclassification that varies between groups in a study.
What is an outbreak?
A sudden epidemic, usually of short duration.
What is an intervention group?
The group deliberately assigned to receive the intervention in an intervention study.
What is the purpose of sensitivity analysis in imputation?
To test the robustness of results when replacing missing values.
What is a random sample?
A group of subjects selected randomly from the general population.
What is the purpose of a case-control study?
To compare individuals with a disease to those without it to identify associations with risk factors.
What is a RANDOM SAMPLE?
A group of subjects selected from the general population in a random manner, where each individual has the same (or a known) probability of being selected.
Define RECALL BIAS.
A type of measurement bias where the ability to remember past events is not independent of disease/exposure status.
What does RELIABILITY refer to in research?
Consistency of instruments’ performance over time and across subjects.
List the types of RELIABILITY.
- Inter-observer
- Intra-observer
- Inter-method / equivalence
- Internal consistency
What is REPEATABILITY?
A test or measurement is repeatable if it yields identical results each time it is conducted under the same conditions.
What is a REPRESENTATIVE SAMPLE?
A sample that resembles the general population from which it was drawn.
Define RESIDUAL CONFOUNDING.
A spurious association due to confounding that persists even after adjustment for the confounder.
What is RESPONDER BIAS?
A type of measurement bias that occurs when information given by participants is not independent of their exposure or disease status.
What is the RESPONSE RATE?
The number of people who completed and returned a questionnaire divided by the total number of people eligible to participate.
What does RESTRICTION mean in epidemiological studies?
A technique used to control for confounding at the design stage by limiting the study to people similar in relation to the confounder.
Define RISK FACTOR.
An environmental exposure, lifestyle, or inherited characteristic associated with an increased or decreased probability of occurrence of a disease.
What is a RISK RATIO?
The ratio of the risk of becoming diseased in the exposed group to the risk of becoming diseased in the unexposed group.
What is SCREENING?
The organized attempt to detect among apparently healthy people disorders or risk factors of which they are unaware.
What is SECONDARY PREVENTION?
Measures to detect pre-symptomatic disease where earlier detection will lead to more effective treatment.
Define SECULAR TRENDS.
Changes in the frequency of a disease or attribute in a population over a long period of time.
What is SELECTION BIAS?
Error due to systematic differences in characteristics between those selected for study and those not selected.
What is SMALL AREA ANALYSIS?
Studying patterns of disease at a local or regional level, useful for local planning.
Define STRATIFIED RANDOMISATION.
A modified method of randomisation where subjects are separated into strata based on key risk factors before being randomly allocated.
What is STRATIFICATION?
The process of separating a sample into subsamples according to specified criteria.
What does SUBJECT refer to in studies?
A person involved as one of the participants in an epidemiological study.
What is SURVEILLANCE in public health?
The systematic, continuous examination of the incidence and spread of a disease or exposure.
Define SURVEY.
An observational investigation in which information is systematically collected.
What is a SUSCEPTIBLE INDIVIDUAL?
An uninfected individual that is able to become infected.
What is a SYSTEMATIC SAMPLE?
The selection of subjects using a pre-determined order, such as selecting every tenth patient.
What is a SYSTEMATIC REVIEW?
A review of scientific evidence using strategies to limit bias in the assembly and synthesis of relevant studies.
Define META-ANALYSIS.
A statistical analysis of results from separate studies leading to a quantitative summary of results.
What is GREY LITERATURE?
Information not published in databases, not produced by commercial publishers, and not peer reviewed.
What is a BOOLEAN SEARCH?
A search technique that uses logical operators to narrow or broaden search results.
What is PUBLICATION BIAS?
The tendency of authors to report positive findings over negative findings or those with no significant results.
Define TERTIARY PREVENTION.
Measures to reduce disability from existing illness and prevent it from worsening.
What is a TIME SERIES in research design?
A design where measurements are made at several different times to detect trends.
What is VACCINATION?
The administration of antigenic material to bring about an active immunological response.
Define VACCINE EFFICACY.
The degree to which a vaccine protects the vaccinated individual from developing the disease.
What does VALIDITY refer to in measurements?
The degree to which a test measures what it purports to measure.
List the types of VALIDITY.
- Criterion
- Concurrent
- Predictive
- Content
- Construct
- Face
What is a VERBAL AUTOPSY?
A method to ascertain the cause(s) of death from close associates about symptoms and circumstances prior to death.
What type of data does a CANCER REGISTER collect?
Information about people diagnosed with cancer, collected directly from hospitals and healthcare professionals.
