31. Epidemiology 2 Flashcards
Define ‘prevalence’
- proportion of individuals in population who have disease of interest at specific instant
- provides estimate of probability/risk that an individual will be ill at a point in time
Equation for prevalence
number of existing cases of disease/total population
What is point prevalence?
prevalence at a given point in time
- point of time may be fixed calendar day or fixed point in series of events like 2nd post-op day of GA for lower 8s
Define ‘incidence’
- quantifies the number of new cases of disease that develop in population at risk during defined time period
Equation of cumulative incidence
number of new cases of disease during given time period/total population at risk
Equation for incident rate
number of new cases of a disease during given time period/total person-time of observation
What is an index?
- numerical value describing relative status of a population on a graduated scale
- with definite upper and lower limits designed to permit and facilitate comparison
- with other populations classified by same criteria and methods
Uses of indices
- to describe the prevalence of disease/condition in population and describe severity of diseases/conditions
- study and compare heath status of individual and population
- to provide data for epidemiological studies
- for planning oral health policy
- to evaluate success of preventative interventions
Desirable properties of Indices
- equally sensitive across scale to changes in disease severity and disease progression
- simple to apply, objective, clear and unambiguous
- should be valid (faithfully record disease supposed to identify)
- should be reliable (consistent and repeatable)
- measurements amenable to statistical analysis
- acceptable to participant
Define ‘valid’
actually measures what test purports to measure
Define ‘reliable’
- consistency and repeatability in hands of an examiner or group of examiners
Define ‘chance’
- a possibility/probability of something happening
- an opportunity
What is chance’s relevance in epidemiology?
- measurements made are nearly always due to random variation
- so are research findings simply due to chance rather than an actual ‘true’ difference/similarity?
Define ‘bias’
- inclination or prejudice in favour of a particular person , thing or viewpoint to influence unfairly
- a systematic error relating to measurement of a variable - e.g way things are measured, way ps are selected, way data were analysed
Define ‘confounding’
- an error in the interpretation of measurement (even measurement is accurate)
- confounder is prognostically linked to outcome of interest and is unevenly distributed between the study groups
How to manage confounding
- randomise
- stratify
- match
- statistical analysis
dmft and DMFT difference
- former is in primary teeth
- both are for caries measurement
What is ICDAS?
- international caries detection and assessment system
- for all levels of caries
What is CPI?
- community periodontal index
- periodontal treatment need
What is IOTN?
- Index of Orthodontic Treatment Need
- Need for Orthodontic Tx
What is RCI?
root caries index
for root caries
What’s Dean’s index for?
fluorosis
5 problems with DMF/dmf
- M and F are assumed to have been carious
- were past treatment decisions to preventative or restorative reasons?
- equal weight is given to D, M, F yet implications for dental health are different
- F teeth score same as M so what’s the point in decayed teeth restored?
- DMF/dmf score is irreversible
Resources in health care are finite. What does this mean?
- need to priortise who receives limited resources according to NEED, not demand
- use index of orthodontic treatment need
- dental and aesthetic component
- higher scores - greater need
- quantifies measurement to recognised scale
Limitations of epidemiological data
- potential for considerable misclassification of exposure status
- use doesn’t take into account many individual factors for example a study into fluoride wouldnt look at personal intake
