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71 Cards in this Set
- Front
- Back
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Prevalence
ex: % of people in dominica with diabetes today |
proportion of persons in a defined population that has the outcome of interest at a defined point in time (both old + new cases)
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Incidence
what are 3 measures used? |
measures frequency of new cases
(risk, odds, rate) |
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Risk
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probability of outcome occurrence in an outcome free population during a specified time period
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Odds
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ratio of probability of getting the disease to the probability of not getting the disease during a given time period
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Rate
aka incidence rate or incidence density |
expresses the # of people or events in relation to the total population at risk
(includes time frame) "person time at risk" |
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age specific rates
vs crude rates |
-used for a specific age group
-rates that aren't age specific |
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case fatality rate
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proportion of cases of a specified cause which die in a specified period of time
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cause specific mortality rate
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# of deaths by a specific cause in a defined population in a defined period of time
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infant mortality rate (IMR)
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# of deaths in children under 1 year of age divided by the # of live births in same time period in a specified population
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maternal mortality rate
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# of maternal deaths divided by the # of woman in the reproductive age (15-49) in a given yr
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perinatal mortality rate
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# of fetal deaths (22wks gestation or more) and early neonatal deaths (0-7days) in a year, in a defined population, divided by the total # of live births and fetal deaths in the same population and time period
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Survival rate
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proportion of survivors in a group usually patients with a dz who survived in a specified period of time
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Rate ratio
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measure of the strength of the association b/w a risk factor and a dz
**exposed/unexposed |
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vehicle
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mode of transport of an infectious agent through the environment to a susceptible host
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vector
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a living carrier= usually an arthropod; that serves as a mode of transport for an infectious agent from an infected host to a susceptible host
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reservoir
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the primary habitat in which an infectious agent survives and reproduces
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carrier
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a person/animal that harbors a specific infectious agent in the absence of discernible clinical disease and serves as a potent source of infection
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asymptomatic carrier
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subclinical throughout the infectious carrier state
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incubationary carrier
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infectious carrier state occurs during the incubation period preceding clinically recognizable disease
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convalescent carrier
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infectious carrier state continues during convalescence when clinically recognizable disease is no longer present
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exposure period
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time during which an individual or group is exposed to source of infection
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incubation period
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time from initial infection (entry of infection) to onset of clinical illness. (usually expressed as the median or arithmetic/geometric mean, min, and max of incubation period)
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Infectious (or communicable) period
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period during which an infected person is able to transmit the infectious agent. (important to know this for various agents in order to impose appropriate control measures)
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latent period
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time from receiving infection to onset of infectiousness. (minimum interval between successive infections in a chain of transmission)
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serial interval or generation time
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interval b/w the same stage of illness in successive cases in a chain of transmission. (only applicable when infection spreads form person to person)
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Common source outbreak
(point vs extended) |
transmission of an infectious agent involving a source that is common to all outbreak-assoc cases
-brief common exposure (1 incubation period) -present over days/wks (may be continuos of intermittent) |
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propagated/progressive outbreak
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series of progressively taller peaks one incubation period apart (not many outbreaks have this classic pattern)
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what is the preferred measure of association for cross sectional studies?
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chi-square test
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Cohort studies
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starting point is definition of a group of people by their exposure status
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Case control studies
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(retrospective study)
starting point is the definition of a group of people with a particular dz or condition (outcome) **ALWAYS analytical |
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Confounders
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"alternative explanation"
-other risk factors that may contribute to an apparent association b/w the exposure of interest and the outcome (may be unknown) |
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Intervention study #1
= field trial |
trials to prevent disease (difficult to carry out)
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Intervention study #2
= clinical trial |
trials to evaluate one or more new tx's for a disease or condition
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Drug trial classification
Phase I |
first drug experiments with human trials, determines single acceptable dose, metabolism, bioavailability, dosage, 20-80pts
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Drug trial classification
Phase II |
initial clinical investigation for tx effect: small scale into effectiveness and drug safety, screening process, about 100-200 pts
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Drug trial classification
Phase III |
Full scale evaluation of tx: after drug is shown to be effective its compared w/ current standard tx
(MOST rigorous and extensive clinical investigation of new tx) |
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Drug trial classification
Phase IV |
Post marketing surveillance: monitoring for adverse effects and long term studies of morbidity and mortality
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Target population
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general group to whom the investigators expect the results of the trial to be applicable
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Experimental population
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subset of the target population selected for the purpose of conducting the survey
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Study population
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those who are eligible and willing to enroll in the trial
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Randomization (allocation to study groups)
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a method which allows chance and only chance to determine the assignment of subjects to various groups (eliminates bias and creates comparable groups)
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Factorial design
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technique used to test two or more hypotheses simultaneously
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Crossover trials
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each subject acts as his/her own control by receiving at least 2 different interventions at different times after a 'wash-out' period
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Blinding/masking
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patient is unaware as to whether he/she is receiving the intervention under study
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Double blind study
(the more subjective the outcome the greater rationale to use this!!! ex: pain) |
when BOTH patient and investigator DO NOT know whether the subject is receiving intervention of control
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Survival analysis
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examines patient survival following diagnosis or following surgical therapeutic procedure or treatment (or from birth, or a major historical event)
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Casual association
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a change in frequency or quality of an exposure results in a corresponding change in the frequency of the disease or outcome of interest
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Random error (chance)
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random variation from sample to sample can account for observed association
**Sample size matters! |
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P-Value
-used in what? |
a measure that often reported from all tests of statistical significance (quantifying the degree of chance variability)
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P-Value definition
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the probability of observing that an effect at least extreme as that observed in a particular study could have occurred by chance alone
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Confidence interval
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gives information (on p-value in terms of deciding whether an assoc is statistically significant or not) "level of variability"
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Bias
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said to exist when some aspect of the design or conduct of the study has resulted in an alternative explanation for the observed results
-deviation from the truth |
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Selection bias
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when there's a difference b/w the characteristics of the people selected for the study and the characteristics of those who weren't
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Information bias
<errors can be introduced by the observer, responder, or instruments used> |
occurs when measurements or classification of disease or exposure are not valid (not measuring what it's supposed to)
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Confounding
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occurs when the effects of two associated exposures/risk factors have not been separated and its incorrectly concluded that the effect is due to one rather than the other
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Interaction/effect modification
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occurs when the presence of one factor modifies the effect of another
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Casuality=
what criteria is used? |
if chance, bias, and confounding don't seem to explain an observed observation, consider a casual assoc.
-Bradford Hill criteria |
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What is the #1 essential of the Bradford criteria?
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The exposure must precede the outcome if the relationship is casual
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Meta-analysis
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a technique used to combine results from various studies
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Screening
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presumptive identification of unrecognized dz or defect by the application of tests, examinations, or other procedures which can be applied rapidly (sorts out well people) NOT Diagnostic!!
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Primary prevention
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targets asymptomatic people to ID early risk factors for the dz so pathologic process can be interrupted BEFORE symptoms develop
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Secondary prevention
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targets persons who are early in the dz process so as to improve prognosis
"PAP smear"= papanicolaou smear>detects HPV before pts develop cervical cancer |
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Tertiary prevention
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targets persons who are developing complications in order to reduce the impact of the sequelae of such complications
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Screening test validity
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extent to which test actually measures what its supposed to measure
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Sensitivity
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ability of the screening test to identify those who are developing the disease
TP/TP+FN |
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Specificity
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ability of the test to give a negative result when those tested are not developing the disease of interest
TN/TN+FP |
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Positive predictive value
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likelihood that someone with a positive test result has the disease
TP/TP+FP |
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Negative predictive value
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likelihood that someone with a negative test result doesn't have the disease
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Reliability
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degree to which the results obtained by a measurement procedure can be replicated
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Standardization/adjustment
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procedure through which a summary rate is produced which takes into account the differences in population structure
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Vital statistics
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systematically tabulated information concerning births, marriages, divorces, separations, and deaths based on registration of these vital events
"statistics of health, sickness, disease, and death |
