Defining Abnormality Flashcards
Define Epidemiology
The study of distribution and determinants of health related states or events in specified populations and application of this study to control health problems
What is health
A state of complete physical, mental and social well- being and not merely the absence of disease or infirmity
What are three criteria for establishing abnormality
Abnormal as infrequent occurrence
Abnormal as associated with disease/death/disability
Abnormal as treatable
Describe the Statistical definition of Normal
Normal distribution:
Frequent (common as normal)
Within 2 SDs above and below mean
Describe the Statistical definition of abnormal
Values beyond 2 SDs above and below the mean
List four reasons that the statistical definition of Abnormal can be misleading
- Some illnesses more prevalent than others
- association with disease may be important only at extreme values
- some extreme values are beneficial
- some illnesses have no threshold at which risk of ill-health/ death starts
What is the equation for Sensitivity of a test for disease according to Gold Standard
a/a+c
Where
a: true positives
c: false negatives
What is the equation of Specificity of a disease according to Gold Standard
Specificity
d/b+d
Where
b: false positives
d: true negatives
What is the equation for percentage true positive values in a test for disease
a/a+b
Where a is true positive
b is false positives
What is the equation for percentage true negative values in a test for disease
d/c+d
Where c is false negatives and d is true negative
What us done to minimize false negatives in the test for disease
Cut-off shifted to minimize false negatives
Continuum shifted to the left
Ie optimise sensitivity
What are consequences of shifting the cut off to minimize false negatives
Specificity reduced
A negative result from a sensitive test rules out the diagnosis
What changes are made to minimize false positives in testing for disease
Cut-off shifted to the right to minimize false positives and optimize specificity
What are the consequences of minimizing false positives by shifting the cut off to the right
Sensitivity is reduced
Positive result from a specific test rules in the diagnosis
For the criterium that states “Abnormal =Treatable”
What is the point at which the individual is designated abnormal
At a point at which treatment leads to better outcome (treatment does more good than harm)
What is the basic premise of epidemiology
Disease does not occur at random, but pattern of disease reflects the operation of underlying factors
What is the significance of understanding the distribution of disease
We can understand the aetiogy of disease and therefore how OR if need to investigate, treat or prevent it
Define descriptive epidemiology
Study of the occurrence and distribution of disease
What is the difference between Descriptive and Analytic Epidemiology
Descriptive Epidemiology identifies and reports on both the frequency and pattern of health events (what who where when)
While
Analytic Epidemiology searches for determinants of health outcomes (how why)
What are the three objectives of Descriptive Epidemiology
Permit evaluation of trends in health and disease
Provide a basis for planning, provision and evaluation of health services
Identify problems to be studied by analytic method
What are the three pillars of Descriptive Epidemiology
Person
Place
Time
“Person” is a pillar of Descriptive Epidemiology
List aspects of Demographic
Age Sex Marital status Ethnic group Race Socioeconomic Status (social class, occupation,employment status, crowding)
“Person” is a pillar of Descriptive Epidemiology
List aspects of Lifestyle/Behavior
Alcohol Smoking Exercise Religion Stress Nutritional Status
Describe the significance of the pillar “place” in Descriptive Epidemiology
Where person was exposed or source of infection
- Geographical boundaries
- Clustering
- Effects of Migration
- International comparisons
