BMJ 1995;311:1372 (18 November)

Letters

Testing should be in all women

EDITOR,--The paper by J Fletcher and colleagues1 was incorrect to conclude that restricting serum screening for Down's syndrome to women aged 30 or over is preferable to screening all women. Firstly, using a 58% detection rate and a 5% false positive rate for all pregnant women instead of estimates applicable to women aged 30 or over (72% and 12%2 3), and, secondly, not comparing screening policies appropriately introduces important errors.

Screening tests involve a trade off between detection rate and false positive rate. To compare screening policies, cut off levels must be set such that among all pregnancies in a community either the detection rate is held constant and the false positive rates compared or the false positive rate is held constant and the detection rates compared. Fewer miscarriages are induced by amniocentesis for each case of Down's syndrome detected if serum is tested in all women than if it . . . [Full text of this article]


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Relevant Article

Using decision analysis to compare policies for antenatal screening for Down's syndrome
J Fletcher, N R Hicks, J D S Kay, and P A Boyd
BMJ 1995 311: 351-356. [Abstract] [Full Text]

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