Testing for risk of a common illness

Much genetic research now focuses on how genes influence our susceptibility to common illnesses such as heart disease or cancer. However, there are only a few instances where genes appear to have a strong influence. Based on these kinds of observations, it seems highly unlikely that there will ever be simple tests for risk of cancer based on single genes1. For example, the BRCA1 and BRCA2 genes have been linked to breast and ovarian cancer but it has long been known that these genes only account for a minority (5-10%) of cases. The tests are helpful for some women with a very strong family history of cancer. For others, it seems that the estimates of risk associated with BRCA1 and BRCA2 are almost certainly too high2. Researchers have recently shown that women with a faulty BRCA gene as well as a strong family history of breast cancer are at higher risk than women with the same genetic make-up and no family history3. Since most estimates of disease risk have come from studies involving women from high risk families, these results are very likely to be skewed. Therefore, having a faulty gene does not necessarily mean that a person will definitely develop cancer since many other genetic and environmental factors are likely to have an influence3,4.

The development of common illnesses is likely to be influenced by very many genes, each one having only a modest impact5. Attempting to understand how a large number of genes interact to influence risk of multi-factorial diseases is a major challenge for researchers6. Given this complexity, some researchers have questioned whether we will ever be able to develop genetic tests that provide accurate predictions7. At this early stage, it is questionable as to whether people should be offered such genetic tests even as part of general medical practice and certainly not in relation to employment.

Examples of tests for common illnesses;

Many tests for common illness are available on the market, especially via the internet.

Examples of tests for common illnesses
Company Tests Marketing strategy
DNA Direct (US) www.dnadirect.com Tests include;
  • Thrombophilia,
  • Untreatable asthma, Early-onset emphysema or COPD
  • Cystic Fibrosis,
  • Breast & Ovarian Cancer
Direct-to-consumer online sales for US and Ireland Residents only - DNA direct have plans to expand to provide a more international service.
Genova Diagnostics (US) www.genovations.com [Formerly Great Smokies Diagnostics Laboratory (GSDL).] Tests include:
  • cardiovascular disease,
  • osteoporosis,
  • detoxification impairments,
  • immunological defects associated with gut associated lymphoid tissue (GALT)
  • chronic inflammatory conditions
 Via alternative healthcare providers (with recommendations for supplements).
GeneLink (US) www.bankdna.com Nutragenetic" and "Dermagenetic" profiles with advice on vitamins and skin creams. Also profiles for the following conditions;
  • bone health,
  • cardiovascular health,
  • lipid metabolism
  • immune response.
  • neuronal health.
  • measure of DNA's ability to repair and protect itself.
Via alliances with other companies, particularly those marketing nutritional supplements.
Interleukin Genetics www.ilgenetics.com Currently one test commercially available  to test for genetic susceptibility to  periodontitis (gum disease)

Under development;

  • coronary artery disease
  • osteoporosis
  • arthritis
  • diabetic retinopathy
  • periodontal disease
Via dentists.
MediChecks World Wide Ltd (UK)http://medichecks.com A wide range of screening and diagnostic tests, including tests for genetic disorders and for Deep Vein Thrombosis (DVT). Via the internet.
Myriad Genetics (US) www.myriad.com. Tests for hereditary (‘familial' cancers). Via health professionals but using advertising to the general public (see Box 3).
Sciona (UK) www.sciona.com. Cellf range of tests include;
  • Heart Health,
  • Bone health,
  • Insulin resistance,
  • Antioxidant and Detoxification
  • and Inflammation health
Marketed in Body Shop stores in Britain in 2001, but now withdrawn. Still available via some private GPs and alternative health clinics.

 

References and further reading:

  1. Make biology compulsory for presidential candidates. Nature Biotechnology 1999; 17: 831.
  2. Barclay, L. BRCA penetrance overestimated in studies of high-risk patients. Medscape Medical News. 21-8-2002. www.medscape.com/viewarticle/440366
  3. Begg CB. On the use of familial aggregation in population-based case probands for calculating penetrance. Journal of the National Cancer Institute 2002; 94: 1221-6.
  4. Genetic testing in insurance and employment: A new form of discrimination. GeneWatch UK. 2001. Buxton, UK.
  5. Zimmern R, Emery J, Richards T. Putting genetics in perspective. British Medical Journal 2001; 322: 1005-6.
  6. Risch NJ. Searching for genetic determinants in the new millennium. Nature 2000; 405: 847-56.
  7. Terwilliger JD, Weiss KM. Confounding, ascertainment bias, and the blind quest for a genetic 'fountain of youth'. Trends in Molecular Medicine 2003; 35: 532-544.

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