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Kaplan: Biostats and Epidemiology Part I > Chapter 1: Epidemiology > Flashcards

Chapter 1: Epidemiology Flashcards

1
Q

Epidemiology

A

study of distribution and determinants of health-related states within a population

Study of how disease often occurs in different groups of people and why

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2
Q

Endemic

A

expected rate of disease over time;

the disease is maintained without much variation within a region.

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3
Q

Epidemic

A

occurrence of disease in excess of the expected rate; usually presents in a large geographic span than endemics

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4
Q

Pandemic

A

worldwide epidemic

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5
Q

Epidemic curve

A

visual description (commonly histogram) of an epidemic curve is disease cases plotted against time; classic signature of an epidemic is a “spike” in time

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6
Q

Rates are usually described as per how many people?

A

per 100,000

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7
Q

Vital statistics are usually per how many people?

A

per 1,000

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8
Q

What is the general equation to determine rates in epidemiology?

A

actual cases/potential cases = numerator/denominator

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9
Q

What is incidence rate?

by definition

A

(IR) rate at which new events occur in a population

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10
Q

Formula for incidence rate?

A

(Number of new events in a specified period/number of persons “exposed to risk” of becoming new cases during this period ) x 10^n

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11
Q

Attack rate

by definition

A

cumulative incidence of infection in a group of people observed over a period of time during an epidemic, usually in relation to food-borne illness.

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12
Q

Attack rate formula?

A

number of exposed people infected with disease/ total number of exposed people

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13
Q

Another name for attack rate?

A

attack ratio

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14
Q

Prevalence

A

all persons who experience an event in a population

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15
Q

Prevalence formula?

A

Prevalence = (all cases of a disease at a given point and/or period/ total population “at risk” for being cases at a given point and/or period)/ 10^n

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16
Q

A case is counted in prevalence (in prevalence pot) until what events occur?

A

until death or recovery occur

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17
Q

Point prevalence

A

compares disease at different points in time in order to determine whether an outbreak is occurring.

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18
Q

Period prevalence

Also what conditions does it focus on acute or chronic?

A

prevalence during a specified period or span of time and focuses on chronic conditions.

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19
Q

Morbidity rate

A

rate of disease in population at risk (for both incident and prevalent cases)

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20
Q

Mortality rate

A

rate of death in a population (incident cases only)

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21
Q

What is crude rate?

A

actual measured rate in a whole population

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22
Q

What is specific rate?

A

actual measured rate for a subgroup of the population (e.g “age-specific or “sex-specific”)

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23
Q

Standardized rate?

A

adjusted to make groups equal on some factor

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24
Q

Another name for standardized rate?

A

adjusted rate

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25
Q

Crude mortality rate formula?

A

Crude mortality rate = deaths/population

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26
Q

Cause - specific mortality rate formula?

A

deaths from cause/ population

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27
Q

Case - fatality rate formula

A

deaths from cause/ number of persons with the disease and/or cause

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28
Q

Proportionate Mortality Rate (PMR) formula?

A

deaths from cause/ all deaths

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29
Q

Describe purpose of PMR.

A

how much a disease contributes to mortality rate (i.e what proportion of the mortality rate is due to that disease)

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30
Q

Purpose of cause-specific mortality rate?

A

how many people in the population are dying from that disease

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31
Q

Purpose of case-fatality rate?

A

how likely are you to die from the disease i.e fatality

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32
Q

The purpose for assessing the crude mortality rate?

A

to know the crude rate of people dying in the population

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33
Q

What is the goal of prevention in medicine?

A

reduce a person’s likelihood of becoming ill or disabled or of dying prematurely.

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34
Q

Primary prevention

A

Taking action to reduce the incidence of disease and health problems within the population, either through universal measures that reduce lifestyle risks and their causes or by targeting high-risk groups.

35
Q

This type of prevention decreases disease incidence?

A

primary prevention

36
Q

This type of prevention prevents recurrence and slow progression of a condition?

A

tertiary prevention

37
Q

Secondary prevention

A

screens for risk factors and early disease, permitting timely and effective intervention and curative treatment.

38
Q

Tertiary prevention

A

focuses on people who are already affected by a disease. The goal is to improve quality of life by reducing disability, limiting or delaying complications, and restoring function.

39
Q

This type of prevention effort decreases disease prevalence.

A

secondary prevention

40
Q

What is the gold standard screening test for HIV detection?

A

Western blot

41
Q

Positive and Negative meaning in screening test refers to what?

A

test result

42
Q

True or False in screening test refers to what?

A

If the test result is truly positive or negative

43
Q

TP

A

tested positive, sick

44
Q

FP

A

tested positive; actually healthy

45
Q

TN

A

Tested negative; actually healthy

46
Q

FN

A

Tested negative; actually sick

47
Q

Sensitivity?

A

probability of correctly identifying a case of disease

48
Q

Formula for sensitivity?

A

TP/(TP +FN)

49
Q

False negative rate formula?

A

1-sensitivity

50
Q

Specificity

A

probability of correctly identifying disease-free persons.

51
Q

Formula for specificity.

A

TN/(TN+FP) = true negatives/ (true negatives + false positives)

52
Q

False positive rate formula?

A

1-specificity

53
Q

If a test has a high specificity, then a positive result indicates the (presence or absence) of a disease?

A

presence of a disease

54
Q

If a test has a high sensitivity, then a negative result indicates the (presence or absence) of disease?

A

absence of a disease

55
Q

Mneumonic for telling the difference between sensitivity and specificity?

A

SN-N-OUT (sensitive test - negative rules out disease)
SP-I-N (specific test-positive rules in disease)

56
Q

A good screening test should have which of the following epidemiological properties?
A. high specificity
B. low specificity
C. low sensitivity
D. high sensitivity
E. high positive predictive value
F. low negative predictive value

A

D. High sensitivity

57
Q

What is PPV?

A

positive predictive value: probability of disease in a person who receives a positive test result. (probability that a person with a positive test is a true positive (i.e has the disease)

58
Q

Negative predictive value?

A

NPV: probability of no disease in a person who receives a negative test result (the probability that a person with a negative test result is a true negative (i.e does not have the disease)

59
Q

Formula for PPV?

A

TP/(TP+FP) true positives/ (true positives + false positive)

60
Q

Formula for NPV?

A

TN/(TN+FN) true negatives/ (true negatives + false negatives)

61
Q

Accuracy?

A

the degree to which a measurement represents the true value

62
Q

Accuracy formula?

A

(TP + TN)/(TP + TN + FP + FN) or

(true positives + true negatives)/ total screened patients

63
Q

The higher the prevalence the (greater or less) the PPV? NPV?

A

greater the PPV; less the NPV

64
Q

The lower the prevalence the greater or lesser the PPV? NPV?

A

less the PPV; greater the NPV

65
Q

Would increasing the incidence have an effect on sensitivity or PPV?

A

Would have no effect on either because a screening test can only detect current presence or absence of disease, not the onset.

66
Q

Selection bias

A

sample selected is not representative of the population

67
Q

Another name for selection bias?

A

sampling bias

68
Q

Solutions for mitigating selection bias?

A

random, independent sample; weight data

69
Q

What is a solution to measurement biases like Hawthorne effect?

A

have control groups

70
Q

Another name for experimenter expectancy?

A

Pygmalion effect

71
Q

What is experimenter expectancy?

A

expectations are inadvertently communicated to subjects who then produce the desired effect

72
Q

Solution for experimenter expectancy?

A

use double-blind design

73
Q

What is lead time bias?

A

gives a false estimate of survival rates (e.g patients seem to live longer with the disease after it is uncovered by a screening test

74
Q

Solution to lead time bias?

A

use life-expectancy to assess benefit

75
Q

What is recall bias?

A

When subjects fail to accurately recall events in the past

76
Q

What is the solution for recall bias?

A

confirmation

77
Q

What is late-look bias?

A

when individuals with severe disease are less likely to be uncovered in a survey because they die first

78
Q

What is the solution to late-look bias?

A

stratify by disease severity

79
Q

What is confounding bias?

A

factor being examined is related to other factors of less interest

80
Q

What is the solution to mitigating confounding bias?

A

combine the results from multiple studies, meta-analysis

81
Q

What is design bias? What is the most common cause of this?

A

when parts of the study do not fit together to answer the question of interest;

most common issue is a non-comparable control group

82
Q

Solution for mitigating design bias?

A

random assignment, i.e., subjects assigned to treatment or control group by a random process

83
Q

Example of Berkson’s bias

A

only using hospital records to estimate population prevalence.

84
Q

Example of nonrespondent bias?

A

when survey participants are unwilling or unable to respond to a survey question or an entire survey

so people in study will be different than people not included and won’t represent the whole

(i.e) if you are researching workload among managers in a supermarket chain and you decide to collect your data via a survey, managers with the largest workload are less likely to answer your survey questions due to constraints on their time.

Kaplan: Biostats and Epidemiology Part I (5 decks)

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