Elsevier

The Lancet

Volume 357, Issue 9257, 3 March 2001, Pages 709-712
The Lancet

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Misconceptions about the use of genetic tests in populations

https://doi.org/10.1016/S0140-6736(00)04136-2Get rights and content

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Genetic penetrance and environmental factors

The prospect of genetic screening for preventable or deferrable disease is becoming real. As the cataloguing of the human genome proceeds, the rate at which specific genes are being implicated in disease processes is increasing. Because of its genetic basis, much interest has centred on identification of genes for cancer and their usefulness in routine screening. Cost-benefit analysis is urgently needed for screening for single-gene diseases versus multigenetic diseases, and for genes of low

Numbers needed to screen

To assess the role of a gene-environment interaction and screening in a population we need to know the penetrance of the genetic trait and its frequency. A useful approach is to combine penetrance and frequency by computing the number needed to screen (NNS) in order to prevent one case of cancer. The calculation is explained with a worked example in the panel.

Table 1 contains a calculation of NNS in high-risk families for a high-penetrant gene (BRCA1). The cumulative (lifetime) risk of breast

Genetic testing or reduction of exposures

The major diseases in western societies are multifactorial. Thus, lung cancer is not wholly attributable to smoking, but to many linked factors of which smoking is one.

Conversely, smoking also contributes to cardiovascular and other chronic diseases. Elimination of a single environmental exposure (eg, smoking) would reduce a large proportion18 of chronic diseases (table 2). Genetic traits, however, can have a different relation with disease; people with the NAT-2-slow genotype have an increased

False metaphors for DNA

Overall, the proportion of diseases attributable to low-penetrant genetic traits is clearly difficult to establish and is probably much lower than the burden of disease attributable to certain environmental agents. Workers generally agree that less than 5% of cancers are attributable to high-penetrant genes,2 although little is known for other chronic diseases. In general, we can expect little from genetic screening of the population, apart from limited groups (usually families) with a

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References (24)

  • R Ottman

    Gene–environment interaction and public health

    Am J Hum Genet

    (1995)
  • J Bell

    The new genetics in clinical practice

    BMJ

    (1998)
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