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69 Cards in this Set

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What are the 4 aims of epidemiology? (DEPCo)
1. DESCRIBE the health staus of populations
2. Explain the etiology of disease
3. Predict to occurrence of disease
4. Control the occurrence of disease
Define descriptive epidemiology
Describes patterns of disease/risk factors in a population
What are the 3 objectives of epidemiology?
1. Evaluate & compare trends in health & disease
2. Planning, provision, & evaluation of health sevices
3. Creation of hypotheses for analytic studies
What are two sources that descriptive data can be from?
1. Routinely collected/ surveillance w/ required reporting of all cases (SEER)
2. Cross sectional studies (BRFSS, NHANES)
What are some characteristics that should be included in describing disease in a population?
1. Person
2. Place
3. Time
What are some characteristics of persons?
1. age
2. sex
3. marital status
4. ethnicity
5. migrant status
6. religion
7. Socioeconomic status
What are some characteristics of place? (Types of place comparisons)
1. International
2. Geographic (in-country) variations
3. Urban/rural differences
4. Localized occurrence of disease
What are some Characteristics of time?
1. cyclic fluctuations
2. point epidemics
3. secular time trends
4. clustering
What is the objective of analytic epidemiology?
Analytic studies- follow descriptive studies, and are used to identify the cause of the health problem
What are descriptive studies used for?
Identifying a health problem that may exist
What are some characteristics of persons?
1. age
2. sex
3. marital status
4. ethnicity
5. migrant status
6. religion
7. Socioeconomic status
What are some characteristics of place? (Types of place comparisons)
1. International
2. Geographic (in-country) variations
3. Urban/rural differences
4. Localized occurrence of disease
What are some Characteristics of time?
1. cyclic fluctuations
2. point epidemics
3. secular time trends
4. clustering
What is the objective of analytic epidemiology?
Analytic studies- follow descriptive studies, and are used to identify the cause of the health problem
What are descriptive studies used for?
Identifying a health problem that may exist
What is prevalence?
Existing cases @ some designated time
What is an incidence rate?
Describes the rate of development of disease over a certain time period
What good (if any) is prevalence?
1. Describing the burden of a health problem in a population
2. Determining allocation of health resources such as facilities & personnel
3. Estimating the frequency of an exposure
What are the 3 elements of an incidence rate?
1. numerator=# of cases
2. denominator = the pop @ risk
3. time = the period the cases occured
IR=(new cases)/(PAR)*(time period)
What are the applications of incidence data?
1. helps in research on the etiology/causality of disease
2. estimates the risk of developing a disease
3. estimate the effects of exposure to a hypothesized factor of interest
What is crude rate?
Rate in the full population
What is specific rate?
Rate in the subgroup (age, sex, race)
Why shouldn't you compare crude rates across differenct populations?
Observed differences in crude rates may be the result of (age, sex) rather than true variations in rates
What is the advantage to specific rates? If you were to look at the crude death rate due to pneumonia in Ohio (an example of cause-specific death rate), what information would a cause & age-specific rates provide?
cause specific would compare people who died of the same disease
Age specific would compare people of the same age group
What are the most important criteria in the results & discussion of a study? (Hill's Criteria for Causality)
Strength, Consistency, Temporality, Biologic gradient, Biologic Plausability, Coherence, Experimental Evidence, Specificity, Analogy
What is the very most important criteria for causality?
Association is not causation
What describes the rate of development of disease over a certain time period?
Incidence Rate
When considering if the results will help in caring for your patient, what questions come to mind?
1. can the results be applied to my patient care?
2. Were all important outcomes considered?
3. Are the likely tratment benefits worth the harms and costs?
What are 3 questions that should be asked when appraising the validity of a study?
1. Are the results of the study valid? (Internal vs. External Validity)
2. What are the results of the study? (magnitude of the study- clinical vs. statistical significance)
3. Will the results help in caring for my patient? (are the results relevant)?
When considering if the results of a study are valid, what questions come to mind?
1. Did the trial address a clearly focused issue? (population studied, intervention given, outcomes considered)
2. Was assignment of patients to treatment randomized?
3. Were all the patients who entered the trial properly accounted for at the end of the trial? (was follow-up complete)
4. Were patients, therapists, and examiners "blinded" to treatment?
5. Were the groups similar at the start of the trial? (similar age, severity of disease, smoking status)
6. Apart from the experimental treatment, were the froups otherwise treated equally? (was follow-up of the same frequency)
When considering what the results of a study are, what questions come to mind?
1. How large was the treatment effect
2. How precise was the estimate of the treatment effect (look for the confidence intervals, P-value)
As the sensitivity of a test increases, what happens to the error rate?
As the sensitivity of a test increase, the false positive error rate rises
If you accept that an observation is causal, the estimate of the impact that a successful preventative program which eliminates the risk factor can be derived from _________________?
Attributable risk
What best characterizes the risk of contracting a certain disease during a given time period?
The incidence rate for that disease in a given period
What is the ability of a screening test to identify non-diseased from among those who actually have the disease?
The specificity of the screening test
What factors of a screening test determine its validity?
Sensitivity & specificity determine the validity
Interpret a p-value of .003
3/1000 probability that it is just by chance given that the null value was true
A case control study report the odds ratio of 7.1 w/95% CI of 2.4, 35.3 your conclusions should include:
the study probably had a small sample size
What is the null value for comparisons & odds ratios?
comparison is 0 (PAR)
odds ratio is 1
Estimate of prevalence for periodontal disease amoung pregnant women n=679 @32% (95%CI = 25, 39) explain meaning of this point estimate & CI in terms of the unknown population parameter:
95% confident that the results will be between 25&39 (sample estimate = point estimate)
Is external validity primarily concerned with valid data measurments?
No, external validity is a study's applicability to a the real world
Do case control studies result in the direct estimate of the incidence of the disease?
No, Case control studies provide an indirect estimate of risk
What does an increase in disease risk with an increase in the amount of exposure define?
A dose response relationship
Does a cross-sectional study use measurements of disease occurence and distribution across differet time periods?
No, A cross sectional study is a single period of observation
Does descriptive epidemiology examine disease occurence and distribution across different time points?
yes
Studies may be done to generate or test hypotheses. What is the best design for testing a hypothesis?
randomized controlled field trial
The risk of aquiring infection beta is 312 / 1000 among the unvaccinated and 7.2 per 1000 among the vaccinated approximately 8% of the population is exposed to the pathogen every year which of the following actions taken to develop policy would be incompatible with the above information. a)reporting a risk reduction of 304.8/1000 attributable to vaccination
b)reporting that the attrubutable risk percent is 50%
reporting a risk reduction of 304.8/1000 attributable to vaccination is GOOD
Reporting that the attrubutable risk percent is 50% NOT GOOD
A study that involves tracking a condition that can recur in individuals over time. What measure would allow the author to make full use of their collected data?
Incidence Density
What would be necessary to report the prevalence of disease X?
The number of cases at a given time
The degree to which the result may be considered relevant to individuals other than the study subjects themselves is called
External validity
Is it possible to have a measure that is valid bu unreliable?
No, a measure that is valid will always be reliable
What is an example of an exposure?
Lifestyle
What is a study that provides a direct estimate of risk?
Cohort study (relative risk)
What is a study that provides indirect estimate of risk?
Cross-sectional case-control (Odds ratio)
What are the uses of prevalence?
1. describe burden of a health problem in a population
2. determining allocation of health resources such as facilities & personnel
3. Estimating the frequency of exposure
What are the applications of incidence data?
1. Helps in research on the etiology/causality of disease
2. Estimates the risk of developing a disease
3. Used to estimate the effects of exposure to a hypothesized factor of interest
How do you calculate an incidence rate?
(# new cases)/(pop @ risk) * time
What does randomization address?
Randomization addresses confounding
What does blinding address?
Blinding addresses bias
What is the ability of the test to identify correctly all screened individuals who actually have the disease (a/a+c)
Sensitivity
What is the ability of the test to identify only nodiseased individuals who actually do not have the disease (d/b+d)
Specificity
What is the proportion of individuals screened positive by the est who actually have the disease (a/a+b)
Positive Predictive Value
What is the proportion of individuals screened negative by the test who do not have the disease (d/c+d)
Negative Predictive Value
Why does prevalence influence the positive predictive value?
When the prevalence of a disease falls, the +PV falls & the -PV rises
How is confounding detected
Confounding occurs when the crude & adjusted measures of effect are not equal (difference of at least 10%)
What is a point estimate?
A point estimate provides the single most likely estimate of the underlying true population parameter or treatment effect
What is a confidence interval?
confidence interval represents the range within which that true effect plausibly lies
Define confounding
some extraneous factor throwing off the estimate of the exposure of interest
How do you control confounding?
1. randomization
2. Restriction
3. Matching