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What physician sees. Clinical horizon. Disease. What physician does not see. Screening. Lesson plan. Lesson plan Number: Public Health Dentistry/ BDS/ public health/screening Name of teacher: Dr Laxminarayan Sonde Target group: BDS Term 4 Number of students: 15
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What physician sees Clinical horizon Disease What physician does not see
Lesson plan • Lesson plan Number: Public Health Dentistry/ BDS/ public health/screening • Name of teacher: Dr LaxminarayanSonde • Target group: BDS • Term 4 • Number of students: 15 • Duration: 1 hour • Date: 6/3/2019 • Time: 9-10 am • Topic: Screening
contents • Introduction • Differences between screening and diagnostic test • Uses of screening • Types of screening • Criteria for screening disease • Criteria for screening test • Summary
Concept of screening Screening has been defined as "the search for unrecognized disease or defect by means of rapidly applied tests, examinations or other procedures in apparently healthy individuals."
Screening and diagnostic tests Screening differs from periodic health examinations in the following respects: 1) capable of wide application 2) relatively inexpensive, and 3) requires little physician-time. In fact the physician is not required to administer the test, but only to interpret it.
Aims and objectives To sort out from a large group of apparently healthy persons those likely to have the disease or at increased risk of the disease under study, to bring those who are apparently abnormal under medical supervision and treatment
Uses of screening a. Case detection b. Control of disease c. Research purposes d. Educational opportunities
a. Case detection • Prescriptive screening
b. Control of disease • Prospective screening
Types of screening • Mass screening • High risk or selective screening • Multiphasic screening
CRITERIA FOR SCREENINGDisease 1.the condition sought should be an important health problem (in general, prevalence should be high); 2. there should be a recognizable latent or early asymptomatic stage; 3. the natural history of the condition, including development from latent to declared disease, should be adequately understood (so that we can know at what stage the process ceases to be reversible);
4. there is a test that can detect the disease prior to the onset of signs and symptoms; 5. facilities should be available for confirmation of the diagnosis; 6. there is an effective treatment; 7 . there should be an agreed-on policy concerning whom to treat as patients (e.g., lower ranges of blood pressure: border-line diabetes) 8. there is good evidence that early detection and treatment reduces morbidity and mortality; 9. the expected benefits (e.9., the number of lives saved) of early detection exceed the risks and costs
Screening test • Acceptability • Repeatability • Validity (accuracy)
acceptability • Painful, discomforting or dimeaning
Repeatability Depends on 3 major factors • Observer variation • Biologic variation • Errors relating to technical methods
Observer variation • Intra observer variation • Inter observer variation
Biologic variation • Changes in the parameters observed • Variations in the way patients perceive their symptoms and answer • Regression to the mean
Errors relating to technical methods • defective instruments • Faulty reagents • Erroneous calibration
validity • To what extent the test accurately measures which it purports to measure • Ability of a test to separate or distinguish those who have the disease from those who don’t
Sensitivity • The term sensitivity was introduced by Yerushalmy in 1940s as a statistical index of diagnostic accuracy. It has been defined as the ability of a test to identify correctly all those who have the disease, that is "true positive".
Specificity It is defined as the ability of a test to identify correctly those who do not have the disease, that is, "true negatives".
