Epidemiology Flashcards

Question

What is specificity?

Answer 1

The true negative rate. This measures the proportion of negative patients who were correctly identified (e.g. disease-test-) = true negative/condition negative Useful for ruling in disease reliably Low Type I error rate "of those who were negative, how many were picked up as negative?"

Answer 2

1-specificity | Represents Type I error e.g. false positive

Answer 3

1-sensitivity | Represents Type II error e.g. false negatives

Answer 4

1-B | = sensitivity

Answer 5

Number of true positives/Number of positive results | "Of those who tested positive, how many truly were positive?"

Answer 6

Number of true negatives/Number of negative results | "Of those who tested negative, how many truly were negative?"

Answer 7

Prevalence of the disease

Answer 8

A tool used to assess the value of performing a diagnostic test. It uses sensitivity and specificity to determine whether a test result usefully changes the probability that a disease exists.

Answer 9

1 - specificity | False positive rate

Answer 10

1 - sensitivity | False negative rate

Answer 11

Probability of the condition being present after the test Calculated by multiplying Pre-test probability by likelihood ratio When test is positive, post-test = PPV When test is negative, post-test = 1-NPV

Answer 12

sensitivity/(1-specificity)

Answer 13

(1-sensitivity)/specificity

Answer 14

An illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or its products from an infect person, animal or reservoir to a susceptible host, either directly or indirectly through an intermediate plant, host, vector of the inanimate environment

Answer 15

Incidence x duration

Answer 16

The time between exposure to an infectious agent and the onset of symptoms/signs of infection

Answer 17

Time period from successful infection until the development of infectiousness

Answer 18

The time when infection can be transmitted to another susceptible host

Answer 19

Time period between successive generations of a disease being spread from person to person

Answer 20

The ability of an agent to cause infection in a susceptible host Measured by: minimum number of infectious particles required to establish infection; proportion of susceptible people who develop infection after exposure

Answer 21

Average number of secondary cases from one primary case. This tells us how fast the infection is spreading Primary case: individual who brings disease into population Secondary case: people infection by primary case

Answer 22

1 then there will be an epidemic | Assumes everyone in population is susceptible

Answer 23

P: Probability of transmission in a contact between infected and susceptible individuals C: Frequency of contacts in the population/number of exposures of susceptible people to infectious partners per unit time D: How long an infected person is infectious for R0 = P*C*D

Answer 24

1. Number of people in that population who are susceptible | 2. Number of people who are immune

Answer 25

The ability of a microbial agent to induce disease | Measured by attack rate

Answer 26

people at risk who get sick/total # at risk

Answer 27

The severity of disease after infection occurs | Measured by case fatality ratio/proportion that develop severe disease

Answer 28

The ability of an organism to induce specific immunity

Answer 29

Host response that protects against against high numbers of parasites (e.g. P. falciparum) without clearing the infection

Answer 30

Threshold of number of immune people in community at which the likelihood of transmission is small enough to prevent an epidemic

Answer 31

The study of a disease cluster or epidemic in order to control or prevent further spread of disease in a population

Answer 32

An event, condition, characteristic or combination of these factors which plays an important role in producing the disease Causality is the relationship between an event (cause) and a second event (effect), where the second event in understood as a consequence of the first

Answer 33

The set of minimal conditions and events that inevitably produce disease in at least some people == complete causal mechanism

Answer 34

One cause amongst a constellation of causes that make up a sufficient cause together. Factors that work together with the necessary cause to produce disease

Answer 35

A component cause which is a member of every sufficient cause for a given disease. This MUST be present for a disease to occur

Answer 36

= Only one component cause e.g. rabies virus | Most causes of non-communicable diseases are neither necessary nor sufficient

Answer 37

1. Is there an association? (measures of association) 2. Is it a true association? (validity - exclude other reasons: chance, bias, confounding) 3. Is the observed association likely to be a causal one?

Answer 38

A third variable which confuses our assessment of the true association between exposure and outcome

Answer 39

- Study design: - -> Randomization - -> Matching - -> Restriction - Data analysis: - -> Measure confounders - -> Adjust for them through stratification or multivariate regression

Answer 40

A small association doesn't mean that there isn't a causal effect, although the larger the association, the more likely that it is causal

Answer 41

Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect

Answer 42

The effect has to occur after the cause!

Answer 43

``` 1 Strength of association 2 Biological plausibility 3 Consistency (reproducibility) 4 Dose-response relationship 5 Coherence (between epidemiological and lab findings) 6 Specificity 7 Temporality 8 Experiment 9 Analogy ```

Answer 44

``` Cheap Easy to manage/arrange Quick Useful for studying rare diseases Useful as a preliminary study when little is known about the relationship between a risk factor and a disease ```

Answer 45

Observational - don't have the same level of evidence as RCT Prone to confounding May be difficult to establish timeline of exposure to disease outcome

Answer 46

Use of routinely available data - cheap Quick Useful preliminary study to identify factors and populations for further investigation with better method

Answer 47

Routine data may not be designed to answer the set question Data may not describe which variable is case and which is effect Prone to confounding

Answer 48

Reliable form of evidence | Can correct for bias, confounding, chance

Answer 49

Limited external validity i.e. findings may not be generalisable High time and cost Potential for conflict of interest Potential for ethical breaches

Answer 50

Can be used to identify causal relationships between variables Can help identify risk factors for developing a disease Recall error is reduced Reliable data is produced - rank high in hierarchy of evidence Can measure large variety of exposures

Answer 51

Expensive to run Requires many years Participants are prone to loss-to-follow-up

Answer 52

Systematic error caused by differences in the accuracy or completeness of recollections retrieved by study participants regarding past events

Answer 53

Existing study subjects recruit future subjects from their acquaintances

Answer 54

Have certain criteria

Answer 55

Using emerging theory in project to drive selection of new participants

Answer 56

Facts are supported by more than a single source of evidence. If you have used multiple sources but not triangulated the data, then you have analysed each source of evidence separately

Answer 57

Different data collection techniques

Answer 58

Different researchers

Answer 59

Different data sources

Answer 60

Different theories

Answer 61

Is question measuring what it is intended to measure? Is wording understood? How do respondents feel about/react to questionnaire? Time taken

Answer 62

Cognitive factors: comprehension, literacy, recall bias Situation and setting in which the measurement takes place: concerns over social desirability, non-participation, social norms, interviewer, privacy etc Factors related to study design: detection bias (prospective study), bias in measuring exposure (case control), period effects (RCT and prospective)

Answer 63

The relevance is obvious Content validity: all the relevant elements are included Consensual validity: experts agree a measurement is valid Some degree of face validity is required, but it can be deceptive, and where possible needs to be supported by criterion validity

Answer 64

Correlation between the measure and another variable, which is suitable for use as a criterion of validity e.g. scale measuring level physical activity can be validated by test of fitness Ideal criterion is the true value In real life, we use a measure which has been tested before and shown to have high criterion validity

Answer 65

The branch of medicine that deals with the incidence, distribution, and possible control of diseases and other factors relating to health

Answer 66

The study of statistics such as births, deaths, income, or the incidence of disease, which illustrate the changing structure of human populations

Answer 67

Number of deaths and DALYs that can be attributed to environmental factors

Answer 68

DALY = # of people with disease x duration of disease (or loss of life expectancy) x severity (0=perfect health, 1=death)

Epidemiology Flashcards

(92 cards)