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35 Cards in this Set
- Front
- Back
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Validity |
A variable is a valid measure of a property if it is relevant and appropriate as a representation of that property |
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Reliability |
Ability to be repeated
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Health |
The state of complete physical, mental, social, and spiritual well-being and not merely the absence of disease or infirmity |
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In order to describe the disease pattern in the population and identify the determinants (exposures, risk factors, etc.) associated with the specific patterns of the disease we need to: |
1. Measure the frequency 2. Measure the strength of the association between exposure and disease |
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Measurement of health and disease is required for: |
1. Preventing disease 2. Promoting health 3. Planning health services |
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Crude rate |
Occurrence on a total population over a certain period of time |
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Specific rates |
Provide detailed information as rates for specific age, religion, race, cause, gender, etc. |
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Adjusted/standardized rates |
Allows comparison among and between populations having characteristics that may differ |
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Crude rate - advantages |
Actual summary rates are readily calculable international comparisons (widely used despite limitation) |
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Crude rate - disadvantages |
Since populations vary in composition (ex. age), differences in crude rates are difficult to interpret |
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Specific rates - advantages |
Homogeneous subgroups shows details, rates useful for epidemiological and public health purposes |
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Specific rates - disadvantages |
Cumbersome to compare many subgroups of two or more populations |
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Adjusted rates - advantages |
Summary statements differences in groups "removed", permitting unbiased comparison |
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Adjusted rates - disadvantages |
Fictional rates absolute magnitude dependent on standard population chosen opposing trends in subgroups masked |
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Standardization |
Controlling for confounding variable, summarizing stratum-specific rations with equal instead of unequal weights per stratum - trying to level the playing field |
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Direct standardization |
Weighting the age specific ratios with the weights taken from the age distribution Z |
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Indirect standardization |
Weighting the age specific ratios with the weights taken from the age distribution in A |
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Prevelance |
Measuring the extent of a prevailing disease burden in a population |
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Prevalence rate (P) is calculated by: |
P = (# of people with the disease at a specific time) / (# of people at risk at the specific time) x 10n ((the multiplier)) |
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Point prevalence |
The proportion of the population at risk affected by the disease at a specific point in time # of existing cases at point in time / # of population at risk at point in time |
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Period prevalence |
The proportion of the population at risk by the disease over a period of time - no population remains stagnant
# of existing cases during a time period / avg. population size during a time period |
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Factors that may influence prevalence |
-Fatality rate of disease -Duration of illness -Incidence rate -Migration (dynamic population) -Reporting -Treatment -Diagnostics |
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Incidence rate/density |
Rate at which population is changing from disease-free status under the force of morbidity/mortality
Measuring the spread of a disease through a population |
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Cumulative incidence |
Cumulative effect of the incidence rate # of new cases during time period / # starting at-risk and disease free |
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Disease free time |
Person-time at risk |
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Analyzing Data |
1. Determine the magnitude of the association 2. Rule out the role of chance in the results by doing confidence intervals and hypothesis testing 3. Rule out confounding by restriction or statistical adjustment for potential confounding variables |
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Properties of the Risk Ratio (RR) |
1. Ranges from 0 - infinity 2. RR = 1 - no association 3. RR > 1 - positive association 4. RR < 1 - negative association |
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Properties of the Odds Ratio (OR) |
1. Regardless of how the data are sampled, the OR will remain the same 2. It has similar properties to the RR in terms of range, magnitude, and statistical significance 3. Under the conditions of a rare disease, the odds ratio will be a decent approximation to the "true" relative risk (RR) |
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Surveillance |
The ongoing systematic collection, analysis, and interpretation of outcome-specific data closely integrated with timely dissemination of these data to those who are responsible for preventing and controlling disease |
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Essential components of a surveillance system |
1. Collection of useful data 2. Analysis and interpretation of data 3. Dissemination of information and analyses back to people involved in control activities |
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Passive surveillance |
-Most common -Generally uses standardized report forms -Targets physicians, ICPs, labs -Lowest completeness of reporting -Least expensive to operate |
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Active surveillance |
-Active, continuing search for cases, may involve phone calls to physicians, review of hospital records, lab records -High level of completeness -Most expensive - usually limited scope -Conflicting reports of cost-effectiveness |
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Sentinel surveillance |
-Uses a sample of providers -Used to identify trends in diseases that occur at high frequency -Less useful for diseases that require follow-up for control -Very timely information -Cost to operate similar to passive (more $) |
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Goals of surveillance programs |
1. To recognize cases or clusters of cases to trigger control activities 2. To assess public health impact of diseases and measure disease treatment 3. To demonstrate need for communicable disease programs and resources and allocation of resources 4. To monitor effectiveness of control measures 5. To identify high risk populations or geographical areas 6. To develop hypotheses about risk factors for disease acquisition and transmission 7. To recognize multi-state clusters and outbreaks to trigger control activities |
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Who reports surveillance data? |
-Physicians -Hospital epidemiologist -Labs -Nurses -ICP |
