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PATH3309 > 5 - Cancer Epidemiology > Flashcards

5 - Cancer Epidemiology Flashcards

1
Q

Epidemiology

A

The study of distribution and determinants of health related states or events (including disease), and the application of this study to the control of diseases and other health problems

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2
Q

Two principles that epidemiology is based on

A
  • Populations (Defined geographically, socially, biologically, time)
  • Comparisons (differences between groups e.g. disease/no disease)
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3
Q

Descriptive epidemiology

A

Examining the distribution of disease in a population, and observing the basic features of its distribution in terms of time, place, and person.

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4
Q

Analytic Epidemiology

A
  • Testing a specific hypothesis about the relationship of a disease to a putative cause, by conducting an epidemiologic study that relates the exposure of interest (determinant) to the disease of interest.
  • Obtain a valid and precise estimate of effect of an exposure on the occurrence of disease and determine if relationship is causal
  • Key feature is inclusion of comparison groups
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5
Q

What is descriptive epidemiology useful for

A
  • Allocating resources
  • Planning programs
  • Hypothesis development
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6
Q

What is analytic epidemiology useful for

A
  • Hypothesis testing
  • Causal inference
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7
Q

Incidence

A
  • Number of new cases in a certain period of time
  • Useful for understanding risk (cumulative incidence) and speed events occur (incidence rate)
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8
Q

Cumulative incidence

A

Disease events per person

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9
Q

Prevalence

A
  • Number of existing cases at a point in time or within a defined period
  • Useful for planning health services
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10
Q

Population at risk

A
  • Cases make up the numerator
  • PAR is the denominator
  • Individuals in the denominator must have the potential to become a case
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11
Q

Crude incidence rate

A
  • Number of cases divided by number in
    population
  • Does not take into account the changes in the age structure of the population (ageing of population)
  • To compare rates over time (or between countries) need to control for age
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12
Q

Age standardised rate (ASR)

A

Calculated by multiplying each age-specific (5 year intervals) incidence rate of a population by a standard population of the same age groups to yield expected number of cases

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13
Q

What is increase in cancers largely attributed to

A

Rise in number of prostate and breast cancers

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14
Q

Reasons for changing pattens of cancer

A
  • Improved diagnoses through screening programs (screening captures all cancers, including dormant cancers that may not cause harm)
  • Latency from past exposures
  • Changing exposures
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15
Q

Screening tests

A
  • Screening tests are performed to detect potential cancers in people who do not have any symptoms of disease.
  • Limited to risk groups
  • Not considered diagnostic
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16
Q

Epidemiology study design hierarchy

A
  • Pre clinical studies
  • Descriptive studies
  • Analytical studies
  • Experimental/intervention
17
Q

Ecological studies

A
  • The data on exposure and outcome are aggregated data rather than individual data
  • Look for correlation between exposure and outcome
18
Q

aggregated data

A

Summary measure of characteristics of whole
populations (e.g. % tobacco sales for each state rather than number of cigarettes purchased by individuals in each state)

19
Q

Ecological fallacy

A
  • The association at aggregate level may not apply at the individual level
  • Ecological, and other descriptive, studies can be hypothesis generating but are NOT hypothesis testing
20
Q

Case control studies

A
  • Starting point is the disease of interest
  • Study begins AFTER the outcome has occurred (generally)
  • Controls don’t have the outcome of interest but ARE from population at risk
  • Proportion of exposed subjects are compared in the two groups
    (odds of exposure – odds ratio)
  • Efficient for rare diseases (eg. cancer)
21
Q

Cohort studies

A
  • Cohort members are disease free at the start (Compare disease incidence between
    exposed and un-exposed)
  • Participants classified according to exposure status and followed-up over time to ascertain outcome
  • Appropriate for rare exposures
  • Temporality (Exposure occurs before observed outcome)
22
Q

Pros of case control studies

A
  • Rare Disease
  • Good for diseases with long latency
  • Multiple exposures
  • Relatively inexpensive
23
Q

Cons of case control studies

A
  • Exposure Hx problematic (Recall, Temporality, Validation)
  • Appropriate control group
  • Difficult to calculate risk
24
Q

Pros of cohort studies

A
  • Rare exposures
  • Multiple outcomes
  • Complete(?) exposure Hx
  • Temporal sequence (Exposure → disease)
  • Calculate incidence/risk
25
Q

Cons of cohort studies

A
  • Expensive
  • Long follow-up
  • Not good for rare disease
26
Q

Limitations of epidemiological research

A

To study the association between a
potential risk factor and a disease one has
to ensure:
- Accurate diagnosis of disease (Disease (mis)classification)
- Accurate exposure assessment (Exposure assessment is a perennial problem)

27
Q

Bias

A

Any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions which are systematically different from the truth.

28
Q

Selection bias

A
  • Recruitment bias
  • Response bias
  • Loss to follow-up
29
Q

Information bias

A
  • Recall
  • Social desirability
  • Interviewer/observer bias
  • Hawthorne effect
30
Q

Confounding

A
  • Exposure: silica dust
  • Outcome: lung cancer
  • Confounding factor (smoking)
31
Q

ABCs of establishing causation

A

Accident (chance), Bias and Confounding

32
Q

Establishing causation

A
  • Strength of association
  • Consistency
  • Temporality
  • Biological gradient (dose response)
  • Plausibility
33
Q

Class 1 carcinogens

A

Carcinogenic to humans

34
Q

Class 2a carcinogens

A

Probably carcinogenic to humans

35
Q

Class 2b carcinogens

A

Possibly carcinogenic to humans

36
Q

Class 3 carcinogens

A

Not classifiable as to its carcinogenicity to humans (not enough info)

37
Q

Class 4 carcinogens

A

Probably not carcinogenic to humans

PATH3309 (12 decks)

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