Epidemiology Flashcards
List the basic types of Epidemiologic studies
- Descriptive epidemiology (distribution, description)
2. Analytical epidemiology (hypothesized causal relationship, evaluating interventions, risk factors)
Recognize primary health outcomes (“the five D’s”)
Death Disease Discomfort Disability Dissatisfaction
** can add destitution (financial cost of illness)
prevalence
proportion of person in population who have the disease at a specific point
= number of existing cases of a disease / total population (at a given time)
describe sensitivity
Sensitivity (ability of a test to correctly identify those with the disease, aka true positive rate)
= True positives/(True positives + false negatives)
What are the major biases that complicate the interpretation of studies of screening results.
- VOLUNTEERISM: people who attend screening differ from those who don’t. The benefits of screening will exaggerate the benefits.
- LEAD TIME BIAIS: in evaluating the benefit of screening on reducing mortality, a bias in the comparison of survival tomes may result if lead time is not taken into account. In a RCT, we have to compare mortality, nor survival.
- LENGHT -TIME BIAIS: Screening will more likely detect those persons having a longer preclinical disease phase resulting in over representation of slowly progressing disease
however something is measured, we want the mesurement to be…
- Validity: does a measurement reflect the truth? (FREE OF BIAS)
- Reliability: precision, reproducibility
- Responsiveness: does it change as the phenomenon changes?
- Interpretable: Do people reading it know what it means?
Incidence
number of NEW events in a population of individuals AT RISK during interval
what are the 2 specific types of incidence mesures ?
- cumulative incidence
2. incidence rate (incidence density)
cumulative incidence
the proportion of individuals INITIALLY FREE of the disease of interest who develop the outcome during a defined time period
CI = # of new cases during a given period/total population at risk
Incidence rate
number of events divided by the amount of person-time observed, measures how quickly people are developing the disease
DI = # of new cases of a disease in a given period of time/total person-time of observation
what’s the link between prevalence, incidence and duration ?
prevalence = incidence x duration
- lower prevalence = high incidence, short duration (people who have the disease die fast)
- higher prevalence = low incidence/long duration (people live with the disease for a long time)
name 2 special types of incidence mesures and why they’re used
- mortality rate
- attack rate (a type of cumulative incidence , for accute epidemis)
why is prevalence mesure useful ?
- most useful for health care providers
- to assess the public health impact of a specific disease within a community
- to project medical care needs for affected individuals
why is incidence mesure useful ?
- assessing exposure disease relationship
- risk factors for disease
what are adjusted rates ?
used to be able to compare rates between two populations that are different in terms of some important characteristics (age structure, sex, etc.)
what would be the best Dx test ?
- valid
- reliable
- inexpensive
- easy to administer
- of minimal discomfort to the patient