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Oral Health Surveys Lect 4 د. ريا جاسم
Scheduling
In any study , the preparation of an orderly schedule for data collection or
carrying out any procedure is very important to avoid wasting time .
The researcher can estimate from a pilot study or from previous experience ,
how much time on average each examination or procedure will take , a daily and
a weekly schedule can then be made for the researcher and school.
Calibrating of examiners
Examiners may differ in their assessment of the oral health status of the
individual , they all should be in close agreement in assessing the status of
population group , when ever an epidemiological survey is undertaken by a team.
it is essential that the participated examiner be trained to make consistent
clinical judgment .
All examiners involved in the survey need to be trained and calibrated .
The objective of training is to ensure that the examiners are thoroughly familiar
with all aspects of the survey making accurate use of any indices involved and
are prepared for any unexpected complication which may arise .
Calibration : is to ensure that the examiner interprets the examination criteria
that is being used accurately and consistently and that if more than one
examiner is involved , all examiners agree in their interpretation of the criteria.
Accurate : Being able to recognize the condition when ever it is present
Consistent : means being able to repeat the same diagnosis when the same
individual is examined more than one time .
Accuracy may be tested by having each examiner look at a series of subjects and
then comparing his findings with those of an expert who has also examined the
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same subjects , this test should be repeated at interval during the course of a
long study .
The objectives of standardization and calibration
:
1-To ensure a uniform interpretation , understanding and application of criteria
for various diseases and condition to be observed and recorded , to facilitate
the achievement of this objective is by defining criteria in clear and precise term .
2-To ensure that each examiner to consistent standard so that the variability
between different examiners is minimized , to achieve this is dependant on
the number of examiners that are taking part in the survey . When only one
examiner is involved, determine how consistently he can apply the diagnostic
criteria by examining a group of at least 20 patients , if the number of errors
is large , he should review his interpretation of criteria and conduct additional
acceptable consistency assessments.
The examiners should attempt to achieve at least 80 % agreement between the
results of duplicated examinations . When the survey is to be conducted by a
group of examiners , to minimize the inter examiner variability 10 % of the
sample should be examined, and achieving at least 80 % agreement .
Consistency should be tested before and during the survey by requiring all
examiners to chart a group of subjects on 2 separate occasions and then compare
the results .Ideally 10 % of all subjects should be examined in each session or
day during the survey should be re-examined to ensure that consistency is
being maintained .
The inaccurate , but consistent examiner is usually more easily improved then
The occasionally accurate but inconsistent examiner .
Consistent inaccuracy is due to misinterpretation of the examination criteria
perhaps due to poor definition , therefore the criteria and index being used
should be looked at as carefully by the examiner .
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Inconsistancy can be improved with practice.
Variability
There are two types of variability :
1- Intra- examiner variability : where one examiner in fact disagrees with
himself or allows his interpretation of the examination criteria to vary over a
period of time e.g. when one examiner viewing the same tooth surface on
2 separate occasions and records the tooth as a caries positive because
he genuinely thinks that it fulfills the criteria for a ' positive score ' and
records it as a 'caries negative ' on the second occasion because this time he
genuinely thinks that it merits a negative score .
If on the other hand , he recorded it as a caries negative on the second occasion
simply because he overlooked it , then he would have committed an error .
In other words , errors can ideally be avoided entirely , but variations between
examiners are always present to some degree in any survey .
2- Inter- examiner variability : when two or more examiners disagree with
each other when confronted with an identical situation .
There are 2 main reasons for variability of examiners :
A-Chronic diseases such as dental caries and periodontal disease
begin as microscopic lesions that can not be diagnosed by clinical method ,
until these diseases proceed and reach a relatively advanced level,it may be
practically undetectable and easily missed
B-Physical, psychological factors such as fatigue , lack of interest in
the study, difficulty in making decisions , variations in visual acuity and
tactile sense, all affect the judgment of examiners from time to time and to
different degrees. No group of examiners will ever agree completely and
consistently on clinical diagnosis, so the objective of training is therefore
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to minimize the inter-examiner variability .
The methods used for achieving this is by :
1-Practice steadily with frequent breaks for discussion of different
points of diagnosis until all examiners have reached a satisfactory level of
consistency and accuracy .
2-Train more examiners than are needed and reject those who can not
meet the standards required for the work in hand .
3-Measuring the variability of each examiner.
4-Modify the index to be used in the survey until all examiners have
reached an acceptable level of accuracy and consistency .
Organization of the survey
Survey personnel : each examiner should be assisted by human recorder who
is able to follow instructions of the examiner ( a record tape is used to check
possible errors in record forms )
Instruments and supplies :
The following instruments and supplies are required for each examiners
1- Blunt probes sickle shaped probe (now we use sharp eyes and blunt probe),
periodontal probe
2- Plane mouth mirror.(disposable kits are now available for single use)
3- Drum .
4- Method for cleaning teeth as gauze or cotton for removing debris from
around the tooth .
5- The lighting should be as consistent as possible through out the survey ,
a light weighted portable examination light can be used if electricity is available ,
if not , use natural light , or other source such as light attached to head of
examiner, or fiber optic light .
6- Mobile unit a light weight portable dental chair with head for the patient
( straight chair )
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* Sufficient number of instrument must be available
Arranging the examination area
The area for examination should be planned and arranged for maintaining
efficiency and ease of operation , the flow of subjects through the examination
should be easy in such a way that the subjects enter at one point and leave at
another and should not be permitted to crowd around the examiner or recorder .
Information recorder
Name, age, sex, date of examination, registration no, ethnic group,socioeconomic
group, occupation and geographic location.It is essentially combined oral health
and treatment assessment form to provide data for each oral health status section
enabling health administration to obtain more comprehensive estimates for
preventive and curative and restorative action and for manpower requirement