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BLOCK A - Molecules to Global Health > Epidemiology > Flashcards

Epidemiology Flashcards

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Organic Chemistry 101 flashcards
1
Q

what is validity?

A

accuracy - does it correspond to what is true

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2
Q

what is reliability ?

A

precision - does it give consistent results when repeated

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3
Q

(reliability/validity):
1. sensitivity
2. specificity
3. likelihood ratios

A

all three are part of validity

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4
Q

what is the gold standard? (2)

A
  • The method that would ideally give 100% correct results
  • Does not exist, we use the best test available
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5
Q

what is pre-test probability?

A

probability of having the disease BEFORE testing

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6
Q

what is post-test probability?

A

probability of disease AFTER test result

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7
Q

are the pre-test and post-test probabilities low or high for:
1. a positive test
2. a negative test

A
  1. pre-test: low, post-test: high
  2. pre-test: high, post-test: low
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8
Q

what is a true positive?

A

positive test + disease positive

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9
Q

what is a false negative?

A

negative test + disease positive

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10
Q

what is a true negative?

A

negative test + disease negative

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10
Q

what is a false positive?

A

positive test + disease negative

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11
Q

what is sensitivity? how do we calculate it?

A
  • true positive rate (positive test +disease positive)
  • proportion of patients with disease who test positive
  • TP / TP +FN (denominator is everyone who is disease positive, regardless of test result)
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12
Q

what is specificity? how do we calculate it?

A
  • true negative rate (negative test + disease negative)
  • proportion of patients without the disease who test negative
  • TN / TN + FP (denominator is everyone who was disease negative, regardless of test result)
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13
Q

what is the predictive value of a positive test? how do we calculate it?

A
  • proportion of patients with positive tests who have the disease
  • TP / TP + FP (denominator is people with positive test, regardless of disease presence)
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14
Q

what is the predictive value of a negative test? how do we calculate it?

A
  • proportion of patients with negative tests who don’t have the disease
  • TN / TN + FN (denominator is people with negative test, regardless of disease presence)
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15
Q

T/F: sensitivity and specificity change with prevalence and incidence.

A

FALSE: they are fixed characteristics

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16
Q

T/F: PPV and NPV change with prevalence and incidence.

A

TRUE

17
Q

As prevalence increases, (increase/decrease)
1. PPV ____
2. NPV ___

A
  1. increase
  2. decrease
18
Q

what do we need to consider when determining pretest probability? (3)

A
  • Prevalence of disease
  • Characteristics of patient pool
  • Info about the patient
19
Q

what is the receiver operating characteristic curve and what do we want it to look like?

A
  • shows what happens to sensitivity and specificity as different cutoffs are being used
  • want curve to be closer to 1 (means test is more accurate)
20
Q

what is epidemiology? (2)

A
  1. the study of disease occurrence in human populations
  2. the study of distribution and determinants of disease frequency
21
Q

Describe the Grand Experiment (3)

A
  • John Snow thought cholera was reproduced in the body and spread through water/food
  • compared 3 districts that had different water companies (randomized)
  • statistical association between water company (contamination level) and death from cholera
22
Q

what are the two types of epidemiology?

A
  1. descriptive epidemiology
  2. analytical epidemiology
23
Q

what is descriptive epidemiology? (2)

A
  • distribution of disease in population
  • description in terms of person, time and place
24
Q

what is analytic epidemiology?

A
  • examine hypothesized causal relationship
  • identify or measure effect of risk factors or health effect of specific exposure
25
Q

what were the 3 high impact studies in epidemiology?

A
  1. framingham heart study: equations for CVD risk
  2. British doctors study: link between smoking and cancer
  3. Nurses’ health study: risk factors for chronic diseases in women
26
Q

what are the 5 D’s (outcomes of disease)?

A
  1. death: bad outcome (mortality)
  2. disease (symptoms, signs, abnormalities - morbidity)
  3. discomfort
  4. disability
  5. dissatisfaction
27
Q

what is the 6th destitution?

A

financial cost of illness (for individuals or society)

28
Q

what are the main epidemiological tools? (6)

A
  1. vital statistics (mortality)
  2. disease registries
  3. notifiable disease
  4. administrative systems
  5. special surveillance systems
  6. community assessments
29
Q

what is prevalence and how do we calculate it?

A
  • proportion of persons in population who have a disease at a specific time point
  • cases / total population
30
Q

T/F: point prevalence and prevalence are two different things

A

FALSE

31
Q

what is incidence?

A

quantifies nb of new cases of disease that develop in population AT RISK during specified interval

32
Q

what are the two types of incidence measures?

A
  1. cumulative incidence (incidence proportion)
  2. incidence rate (incidence density)
33
Q

T/F: when calculating incidence of endometrial cancer (uterus), we include men and women

A

FALSE: only women are at risk since only they have a uterus!!

34
Q

what is cumulative incidence (incidence proportion)? how do we calculate it?

A
  • proportion of individuals initially free of the disease who develop it during a time period
  • nb new cases / population at risk
35
Q

T/F: cumulative incidence is the probability or risk of developing a disease

A

TRUE

36
Q

what is incidence rate (density) and how do we calculate it?

A
  • nb of events divided by the amount of person-time observation
  • new cases / total person-time of observation
37
Q

T/F: incidence rate measures how quickly people are developing a disease

T/F: incidence rate is the TRUE rate because it measures number of cases per unit time

A

TRUE for both

38
Q

how are prevalence and incidence rate related?

A

prevalence = incidence rate x duration

39
Q

what are the special types of incidence measures? (2)

A
  1. mortality rate
  2. attack rate (cumulative incidence)
40
Q

when are prevalence and incidence most helpful?

A
  • prevalence is most useful for health care providers (assess public health impact)
  • incidence is most useful to assess exposure disease relationship and risk factors
41
Q

DO SOME PRACTICE QUESTIONS

A

DO SOME PRACTICE QUESTIONS

BLOCK A - Molecules to Global Health (5 decks)

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