Term
| in this type of study subjects are chosen on the basis of exposure status and followed to assess the occurrence of disease |
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Definition
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Term
| A special type of prospective cohort study in which investigators assign the exposure to individuals preferably at random |
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Definition
| experimental study option |
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Term
| cases with the disease and controls who generall do NOT have the disease are chosen and past exposure to a factor is determined is what type of study? |
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Definition
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Term
| choice of study design depends on (4) |
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Definition
state of knowledge
frequency of exposure and dz
time, cost, & feasability
advantages & disadvantages |
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Term
| what 3 alternatives need to be RULED OUT in epidemiologic study? TEST ? |
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Definition
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Term
| THE 2 QUESTIONS THAT MUST BE ASKED WHEN EVALUATING AN EPIDEMIOLOGIC STUDY? |
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Definition
is the observed association CAUSAL?
is the association VALID? |
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Term
| when assessing if the observed data in a study is valid you must do what three things? |
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Definition
rule out random error (chance)
rule out bias (systemic error)
rule out confounding (mixing of effects) |
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Term
| P value and confidence intervals quantify what? |
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Definition
| the amount of random error |
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Term
| any systematic (non random) source of error in the determination of the association b/t the disease and exposure is what? |
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Definition
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Term
| the type of bias that results in the selection of subjects |
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Definition
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Term
| bias caused by how information was obtained? |
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Definition
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Term
| a mixing of effects b/t the association of the disease, the exposure and a thired factor is what? |
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Definition
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Term
| a group of people with a common characteristic like age, race, or sex? |
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Definition
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Term
| the two types of population are based on whether the the membership is ?____ or _____ |
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Definition
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Term
| in this type of population the membership is permanent and defined by an event? |
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Definition
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Term
| in this type of population the membership is transient and defined by being in or out of a "state"? |
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Definition
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Term
| an population of 5 YEAR cancer survivors is an example of what type of population? |
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Definition
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Term
| THE RESIDENTS OF THE CITY OF SAVANNAH ar an example of what type of population? |
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Definition
| dynamic (because membership is transient) |
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Term
| measures of disease frequency should take three things into account? what are they? |
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Definition
1. number of individuals affected with the
2. size of source population
3. length of time the population was followed |
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Term
| to measure the disease frequency of AIDS in two cities? what 3 things must be considered? |
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Definition
1.# of new AIDS CASES
2.time period in which new AIDS cases occured
3.size of the source population the new AIDS cases arised. |
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Term
| the division of one number by another, (numbers dont have to be related) |
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Definition
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Term
| the numerator is a subset of the denominator. (often expressed as a percentage) |
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Definition
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Term
| time is an intrinsic part of the denominator (often most misused) |
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Definition
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Term
| THE number of existing cases of a disease divided by the number in total population is what variable? |
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Definition
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Term
| a city A has 7000 people with arthritis on Jan 1st 1999 & the population of city A is 70,000? what is the point prevalence (P) |
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Definition
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Term
| THE number of NEW cases of disease that can occur more than once, usually initial occurence of disease? |
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Definition
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Term
| what are the 2 types of incidence? |
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Definition
incidence rate IR
cumulative incidence CI |
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Term
| the number of new cases of disease divided by the number in candidate population over a specified period of time (during a specified time is what?) |
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Definition
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Term
| 10 cases of SIDS out of 1000 live births over 1 years time = a CI of ? |
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Definition
| 10/1000= 1% cumulative incidence over 1 year |
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Term
| a cumulative incidence calculation assumes what_________________? |
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Definition
| that you have followed the entire population for the ENTIRE follow up period? |
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Term
| which type of incidence does not make assumption for complete follow up? |
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Definition
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Term
| HE NUMBER OF NEW DISEASE DIVIDED BY THE PERSON-TIME PERIOD OF OBSERVATION IN THE CANDIDATE POPULATION? |
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Definition
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Term
| why is IR a measure of true rate? |
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Definition
| because it directly intergrates time into the denominator |
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Term
| ways to convert to person years (PY) |
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Definition
100 people followed 1 yr each= 100py
10 people followed 10 yr each=100py
50people followed 1 yr + 25 people for 2 yr= 100py |
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Term
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Definition
| # of cases / person time period |
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Term
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Definition
| prevalence/ (1-prevalence) |
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Term
| what can you conclude if: incidence is LOW but duration is long? |
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Definition
| prevalence is relatively high |
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Term
| if incidence is HIGH but duration is SHORT, you can conclude what? |
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Definition
| prevalence is relatively low |
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Term
| If the prevalence of a disease is low (<10%) the equation simplifies to ____? |
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Definition
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Term
| the total number of deaths from all causes per standardized population per unit of time is what? |
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Definition
| crude death (mortality) rate |
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Term
| total number of live births per year standardized population denominator (e.g per 1000 women of childbearing age) |
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Definition
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Term
| number of death in infants under 1 year of age per year divided by standardized population denominator (per 1000 live births) |
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Definition
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Term
# cases of disease that develop during
defined time period divided by # in pop. at risk at start
of period (usually used for infectious disease outbreaks) |
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Definition
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Term
# cases of disease that develop during
defined time period divided by # in pop. at risk at start
of period (usually used for infectious disease outbreaks) |
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Definition
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Term
# of deaths from a specific
disease or disorder during a defined period of time
divided by the # cases of disease / disorder |
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Definition
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Term
number of living cases of a disease /
disorder for a defined period of time divided by the total
number of cases of the disease / disorder |
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Definition
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Term
| does the Overall rate of disease/outcome in an exposed group says nothing about whether exposure is a risk factor for or causes a disease or other outcome |
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Definition
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Term
| the 2 main options for comparison groups are to calculate: |
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Definition
1. the ratio
2. the difference |
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Term
| the rate/risk ratio is also known as the what? |
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Definition
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Term
| what does the risk ratio compare? |
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Definition
| compares the disease occurence among exposed individuals to the comparison group which is usually unexposed |
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Term
| an RR (rate risk ratio of 1.0) tells you what? |
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Definition
| there is no association b/t exposure and disease |
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Term
| an RR (rate/risk ratio of 2.0) tells you what? |
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Definition
| there is two times the risk of dz in the exposed compared to the unexposed |
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Term
| what does a RR of 1.6 tell you? |
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Definition
| that there is a 1.6 times risk of dz in the exposed compared to the unexposed or 60% increased risk of disease in the exposed |
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Term
| difference measures are calculated by? |
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Definition
| Comparing disease occurrence among the exposed with the disease occurrence among the unexposed comparison group by subtracting one from the other |
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Term
| risk/rate difference is also known as ? |
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Definition
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Term
| risk/rate difference is also known as ? |
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Definition
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Term
| a rate/risk difference or attributable risk of 0 means what? |
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Definition
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Term
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Definition
| number of persons to treat to prevent one specific case of the disease or outcome of interest. |
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Term
| Diagnostic screening is only relevant under what 4 circumstances? |
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Definition
1. if the dz is common
2. testing is sensitive,& specific
3. early tx improves outcomes
4. cost effectiv |
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Term
| the equation for TRUE POSITIVE RATE (TP) |
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Definition
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Term
| THE PROBABILITY THAT A DISEASED INDIVIDUAL WILL BE IDENTIFIED AS SUCH BY THE TEST IS ? |
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Definition
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Term
| THE PROBABILITY THAT AN INDIVIDUAL W/O THE DISEASE WILL BE IDENTIFIED AS SUCH IS ? |
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Definition
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Term
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Definition
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Term
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Definition
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Term
| TO not "miss anyone" it is best to use cut-off points that__________ |
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Definition
| have increased sensitivity and decreased specificity |
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Term
| to make sure no member of the tested population is erroneously labled use test that have______________________ |
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Definition
| decreased (low) sensitivity and increased (higher) specificity |
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Term
| the positive and negative predictive values for a given test depend on what? |
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Definition
| the PRETEST PROBABILITY of the condition of interest as well as sen & specificity |
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Term
| positive predictive value eq: |
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Definition
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Term
| NEGATIVE PREDICTIVE VALUE EQ: |
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Definition
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Term
| ARE sensitivity and specificity altered by the pretest probability of the condition? |
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Definition
| NO, positive and negative predictive value are however altered |
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Term
| Likelihood ratio for a negative test = |
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Definition
| 1-sensitivity/ specificity |
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Term
| likelihood ratio for a positive test + |
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Definition
| sensitivity/1-specificity |
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Term
| the 2 basic approaches to improve confirmatory accuracy in most cases are? |
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Definition
1.parallel testing
2. serial testing |
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Term
| performing a PSA/DRE all at once is an example of what sort of testing? |
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Definition
| parallel testing (increases sensitivity and negative predicted values of results |
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Term
| what effect does serial testing have on test value results? |
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Definition
| serial test increase specificity and positive predicted value |
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Term
| what test increases sensitivity and negative predicted value |
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Definition
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Term
| the earlier in a disease's natural hx it is detected, the longer will be the survival from the time of dx, even if there is no difference in tx effect defines what? |
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Definition
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Term
| when screening detects dz that would have otherwise never become clinically detectable and remains stable and asymptomatic this is an example of ? |
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Definition
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Term
| when cases are diagnosed by screening that may be destined for a more favorable evolution regardless of tx this describes what |
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Definition
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