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Statistical and pharmacoeconomic issues for Alzheimer's screening
Author(s) -
Ashford J. Wesson,
Kraemer Helena C.,
Tinklenberg Jared R.,
O'Hara Ruth,
Taylor Joy L.,
Yesavage Jerome A.
Publication year - 2007
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2007.03.004
Subject(s) - test (biology) , value (mathematics) , incidence (geometry) , medicine , actuarial science , statistics , mathematics , psychology , economics , paleontology , geometry , biology
The principles for determining whether a screening test s appropriate requires several considerations [1]. A comrehensive view can be developed from considering a mathmatical analysis of the costs and benefits of a clinical valuation. A mathematical calculation of the “cost-worthiness” of a est will give a direct assessment of whether a screening test hould be implemented. To calculate cost-worthiness, the folowing factors must be considered: I incidence (new occurences each year, by age); $T cost of test, time to take (for ubject and Tester); Se sensitivity of test True positive/I; p specificity of test True negative/(1 – I); $B benefit f a true-positive diagnosis; $C cost of a false-positive iagnosis; True negative (real peace of mind) (no money); alse negative false peace of mind (no price); W ($B I Se) – ($C (1 – I) (1 – Sp)) – $T. f $W is greater than zero, then the test is cost-worthy. As an example of implementing this equation by using onservative estimations, consider the following variables: I ncidence of Alzheimer’s disease (increase from 1/1000 per ear at age 62, doubling every 5 years); Se 0.9; Sp 0.9 tests of less than 5 minutes appear to be able to reach this evel) (contrasted with a perfect test, Se and Sp 1, and a less obust test, Se and Sp 0.8); $B vary linearly from $25,000 n a 50-year-old patient (considering the value of a 6-month elay of nursing home placement with timely medical treatent) to $0 in a centenarian patient; $C a false positive ould require a $500 clinic visit to disprove the dementia uspicion. It is apparent from the graph (Figure 1) that even with hese conservative estimates, a cost for screening for deentia of $25 per year is justified from 75 years of age until lder than 95. Better or less expensive tests or more efficient linic visits could lead to recommendations as low as 55 ears of age, and more valuable treatments would similarly educe the age for recommending broad application of creening tests. Risk factors can be introduced to the cost-worthiness quation as they affect incidence “I”. For example, APOE enotype can greatly affect risk [2], and it would be justified d