2. the presumptive identification of
unrecognized disease or defect by the
application of tests, examinations or other
procedures which can be applied rapidly to
sort out those who probably have the disease
from those who probably do not

3. Criteria for screening

5. Characteristics of a diagnostic test

6. Accuracy of a screening
 The test should give a true
measurement of the attribute under
investigation and provide consistent
results in repeated trials more over it
should have high sensitivity and
specificity for the disease in question

7. Specificity—The ability of a test to give a positive
finding when the person is tested truly has the
disease under study
Sensitivity—the ability of a test to give a negative
finding when the person tested is free from the
disease under study
sensitivity and specificity both expressed in %

8. CALCULATING SPECIFICITY AND SENSITIVITY
The fourfold contingency table is used

9. SPECIFICITY

10. SENSITIVITY

11. PREDICTIVE VALUES
 Positive Predictive Value is the probability that patients with a
positive screening test truly have the disease

12.  Negative Predictive Value is the probability that patients with a
negative screening test truly do not have the disease

13. REFERENCES
http://gim.unmc.edu/dxtests/howto.htm
http://www.fpnotebook.com/Prevent/Epi/TstSnstvty.htm
http://sphweb.bumc.bu.edu/otlt/MPH-Modules/
EP/EP713_Screening/EP713_Screening5.html#positiveandneg
ativepredictivevalue
Thorner and Remein. Principlesand Procedures in the Evaluation of
Screening for Disease, US Department HEW, Public Health Monograph
No. 67, 1961