1. MEASUREMENT OF ORAL DISEASE Chapter 14

2. EPIDEMIOLOGY AND PRACTITIONER
A patient is more likely to exhibit a particular disease if he/she exhibits certain characteristics
Example: an elderly man who smokes and drinks heavily is more at risk of oral cancer than one who does not
CAN A PRACTITIONER GENERALIZE FROM THE RESULTS OF A CLIENT’S TREATMENT TO THE POPULATION AT LARGE?

3. EPIDEMIOLOGY & THE PRACTITIONER
During diagnostic examination, a dental practitioner looks for existing disease and looks ahead for possibility of future disease
Appropriate controls and designs allow for effective prevention and treatment

4. INFLUENCES IN EPIDEMIOLOGY
HEREDITY
BIOLOGY
PHYSICAL ENVIRONMENT
SOCIAL ENVIRONMENT
LIFESTYLE

5. METHODS OF MEASURING ORAL DISEASES
COUNTS
PROPORTIONS
RATES
INDEXES

6. COUNTS The simplest form of measuring oral disease
Most useful with unusual conditions of low prevalence
Becomes less useful as prevalence escalates

7. PROPORTIONS
A count can be transformed into a proportion by adding a denominator, thus determining prevalence
Example: 22 cases of cancer in a population of 845 men (ages 55-65) yields a prevalence of 2.6%

8. RATES
A proportion that utilizes a standardized denominator including a time dimension
Example: infant mortality rate for white children declined
( per 1000 live births)
( per 1000 live births)

9. REVERSIBLE INDEX IRREVERSIBLE INDEX
measures cumulative conditions that CAN be reversed
measures cumulative conditions that CANNOT be reversed

10. PROPERTIES OF AN IDEAL INDEX
VALIDITY
RELIABILITY
CLARITY & SIMPLICITY
QUANTIFIABILITY
SENSITIVITY
ACCEPTABILITY

11. VALIDITY Measures what it is intended to measure
CONTENT VALIDITY - measures extent to which an instrument thoroughly represents knowledge in the selected content area
CRITERION VALIDITY - compares newly developed instrument with pre-existing valid and reliable instrument in order to evaluate accuracy and appropriateness of new instrument

12. RELIABILITY Measures consistently at different times
Example: Two examiners must find the same 3 occlusal caries on 1st molars in Child A. If they examine Child A an hour later, they should still find the same occlusal caries as detected previously

13. INTRARATER & INTRAEXAMINER RELIABILITY
Each examiner is scoring equivalently (consistently) time and time again with each measurement taken
This has been described as “the extent to which the same investigator remains consistent in scoring techniques when using a data collection instrument” (Drury)
Example: examiner records conditions in a group of 10 to 20 individuals and then repeats the process a few hours or days later

14. INTERRATER & INTEREXAMINER RELIABILITY
Consistency exists between examiners
If different examiners were to measure the same population, the data (results) collected would be the same
Examiners must have an initial and continued agreement on interpretation of evaluative criteria
Training with repeated use of dental index on subjects is required to achieve reliability
Calibration among examiners ensures that each will measure the data in the exact same manner

15. TYPES OF SCALES USED TO MEASURE DISEASE
NOMINAL – observations fitted into mutually exclusive categories
ORDINAL – ranking characteristics
INTERVAL – equal intervals along scale – has no absolute 0
RATIO – presence of absolute 0
Nominal – republicans/ democrats; males/females; smokers/non-smokers; pass/fail; normal/abnormal
Ordinal – student A highest score 1/ student B second best 2; strongly disagree, disagree, agree, strongly agree (Likert scales)
Interval – Fareinheit thermometer
Ratio – age, weight, height

16. TYPES OF SAMPLING METHODS IN THE COMMUNITY
PROBABILITY
NONPROBABILITY
SIMPLE RANDOM
STRATIFIED RANDOM
CLUSTER
SYSTEMATIC
QUOTA
CONVENIENCE

17. NONPROBABILITY SAMPLING
Different units in the population have equal probabilities of being chosen
NONPROBABILITY SAMPLING
Cannot identify or do not have access to the entire population of interest

18. SIMPLE RANDOM SAMPLING
Each item or person in the population of interest has an equal chance of being selected
A fair way to select a sample
Not the most statistically efficient method of sampling since you may not get good representation of subgroups in a population.

19. STRATIFIED RANDOM SAMPLING
Method of sampling used to represent subgroups proportionately in the sample when they are known to exist in the population
Would you rather use Stratified Random Sampling in the community over Simple Random Sampling? If so, why?

20. CLUSTER SAMPLING
Drawback: When sampling a population that is disbursed across a wide geographic region, a lot of ground geographically will have to be covered in order to get to each of the units sampled.

21. SYSTEMATIC SAMPLING This is a random sampling with a system
It spreads the sample more evenly over the population
Example: drawing every ‘nth” subject from a list of the total population
Example: want to sample 8 houses from a street of 120 houses; every 15th house is chosen

22. QUOTA SAMPLING
Like stratified sampling, the researcher first identifies the stratums and their proportions as they are represented in the population
Then convenience or judgment sampling is used to select the required number of subjects from each stratum
Quota Sampling is a type of CONVENIENCE SAMPLING

23. CONVENIENCE SAMPLE
Subjects are recruited as they arrive and the researcher will assign them to demographic groups based on variables like age and gender.
When the quota for a given demographic group is filled, the researcher will stop recruiting subjects from that particular group.
This type of method is often used during preliminary research efforts to get a gross estimate of the results – saves cost and time
This is done when access to total population is not feasible

24. EXAMINATION TO CHECK RELIABILITY
Consist of repeat examinations only hours apart; too close together for real change to occur
OCCURRENCE OF NEGATIVE & POSITIVE REVERSAL
Occur over a period of time long enough for real change to occur

25. CRITERIA FOR IDEAL DIAGNOSTIC TESTS
Simple
Inexpensive
Acceptable to Client
Valid
Reliable
Sensitive
Specific