“ Genetic testing includes rarer Mendelian single gene inherited disorders such as cystic fibrosis or haemophilia, genetic testing on cancers, cytogenetic testing for chromosomal disorders such as Down syndrome or balanced chromosomal rearrangements associated with infertility. Though tests are limited, there is also a lot of interest in the genetic basis of more common diseases.”
“ For example, children with developmental delay; a microarray test has come into clinical practice in the last 3-4 years that is replacing chromosomal karyotype screening. Microarrays are zoomed in tests that look at small deletions or duplications of pieces of chromosomes, which has increased the diagnostic yield in these children from 3-4 % to about 10 %. Developmental delay or autistic spectrum disorder affect around 3 % of children, and the test looks for a contributory factor to the child’ s presentation.”
The technologies to emerge from the human genome project fuelled initial excitement but genetics has suffered a reality check in the clinical world.
“ When new things come in, they can be overstated. Genome-wide association studies so far have provided a lot of useful information on the pathways that underlie common disease but they haven’ t yet provided clinically useful tests that predict risk better than a good family history. Some
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direct-to-consumer companies, mainly overseas, use this genome-wide association research to give people a risk profile for common diseases. Clinical labs don’ t offer this testing because clinical utility is currently low. For example, a test that shows you have a 1.5 greater than background risk of developing Crohn’ s disease may not alter patient management. Compare this to a BRCA1 mutation which may mean you have an 80 % lifetime chance of developing breast cancer; this is significantly more than the 10 % risk amongst all women and can lead to surveillance or treatment decisions.”
The emerging technologies have made it easier to research cancers.
“ Cancers are really an accumulation of genetic mutations in growth and apoptosis pathways; these mutations can help guide treatment. Researchers are carrying out‘ cancer genome mapping’ where they are trying to sequence the DNA from a lot of cancers from different patients to try and find out common changes that might be targeted. There will be a big growth in testing for cancer mutations that can help direct treatment,” James suggested.
With genetic counsellors and clinical geneticists also in short supply, a growing need for genetic scientists in labs, various new tests vying for position on the MBS schedule, and varying advice about whether current tests should be restricted to specialists( currently, Factor V, haemochromatosis, a fleet of cytogenetic or chromosomal tests, and microarray testing are not), and disparity of funding between states, there is much for the experts to work through. Whatever happens, there is much for us all to learn.
“ A greater education in genetics is needed, starting from medical school and through general practice and the specialties – every single branch of medicine involves genetics, and there will be growing interest in genetic testing. I would like to see a point where nonspecialists have enough knowledge regarding certain disorders so they are comfortable counselling a patient and can do it safely. I don’ t think we are there yet.” �
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