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Detection rates and false positive rates for Down's syndrome screening: how precisely can they be estimated and what factors influence their value

Dunstan, Frank David John, Gray, J. C., Nix, Arthur Barry and Reynolds, T. 1997. Detection rates and false positive rates for Down's syndrome screening: how precisely can they be estimated and what factors influence their value. Statistics in Medicine 16 (13) , pp. 1481-1495. 10.1002/(sici)1097-0258(19970715)16:13%3C1481::aid-sim575%3E3.0.co;2-0

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Abstract

Down's syndrome screening is currently carried out using a combination of biochemical markers measured in maternal serum samples; these include MSAFP, Total hCG, uE3 and Free beta-hCG. Recently a number of papers have compared the effectiveness of different combinations of these markers. Some recommend MSAFP, Total hCG and uE3 (triple test) while others advocate MSAFP and Free beta-hCG (double test). The cases put forward to support these tests rely on estimated detection and false positive rates for the proposed test. A recent paper by Wright used simulation techniques to estimate the effects of sampling error on such error rates. In prospective studies there are two methods commonly used for estimating these rates. We obtain formulae for the standard deviations of these estimates and show that one of them always gives a smaller standard error than the other. We also show that in such studies the accuracy of estimating detection rates and false positive rates depends not only upon the method of calculation but also on the age distribution of pregnant women and the parameters used to calculate patient specific risk. We show that these effects can result in estimation errors of such magnitude that many observed differences in detection rates could be of questionable significance, a conclusion also reached by Wright.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Medicine
Subjects: R Medicine > R Medicine (General)
R Medicine > RZ Other systems of medicine
Publisher: Wiley-Blackwell
ISSN: 0277-6715
Last Modified: 05 Nov 2019 04:10
URI: http://orca-mwe.cf.ac.uk/id/eprint/63849

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