Which of the following characteristics is not of much impoance in a screening test
High specificity All are impoant attributes of screening test but among them high specificity is less impoant as Park states -'Screening test is not intended to be a diagnostic test. It is only an initial examination. Those who are found to have positive test results are refen-ed to a physician for fuher diagnostic work-up & treatment. High specificity is a necessary attribute for a diagnostic test. Below are given the differences between screening and diagnostic tests. Screening test Diagnostic test * Done on apparently healthy Done on those with indications or sick (asymptomatic) * Applied to groups Applied to single patients, all diseases are considered * Test results are arbitrary and final Diagnosis is not final but modified in light of new evidence, diagnosis is the sum of all evidence 4. Based on one criterion or cut-off Based on evaluation of a number of symptoms, signs and point (e.g., diabetes) laboratory findings Less accurate More accurate 6. Less expensive More expensive 7. Not a basis for treatment Used as a basis for treatment 8 The initiative comes from the investigator or agency providing care The initiative comes from a patient with a complaint Criteria for Screening test Screening test must satisfy the criteria of - acceptability - repeatability - validity - simplicity - safety - rapidity - ease of administration - low cost 1. Acceptability - Considering that screening tests are applied on asymptomatic people in large numbers, a high rate of people cooperation is needed. Thus the tests should be acceptable to the people. In general, tests that are painful, discomfoing or embarrasing (eg. rectal or vaginal examinations) are not likely to be acceptable to the population in mass campaigns. 2. Repeatability (Precision or reproducibility) - means that the test must give consistent results when repeated more than once on the same individual or material under the same conditions. 3.Low cost - A screening should be inexpensive. As a screening test has to be applied on millions of people to identify a small percentage who have early disease or its precursors, an expensive test however good, cannot justify use of restricted financial resources that has to be used for fuher diagnostic workup and t/t of those screened on positives. 4. High safety margin - This is an attribute of any test, whether diagnostic or screening. Moresoever for screening as screening tests are to be applied on millions of asymptomatic people and any adverse effect would bring whole process into disrepute. iims IN/nee answers & explanations -- May 2007 5. Validity - It expresses the ability of a test to separate or distinguish those who have the disease from those who do not - Validity has two components - sensitivity & specificity - An ideal screening test should be both highly sensitive and highly specific. But this is seldom possible and a compromise has always to be made.
Low cost
High safety margin
High sensitivity
High specificity