“ 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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