Purposes of genetic tests

10.7 Genetic testing can be divided into three broad categories based on the purpose of the testing, namely, medical testing, identification testing and kinship testing. These categories are not fixed: genetic testing sought for one purpose can sometimes reveal unintended information, such as where medical testing reveals incidental information about parentage or lack of parentage.

10.8 There are numerous reasons for seeking a genetic test. Although the description given to a test varies according to context and user, the following are the most common types of genetic tests referred to in this Report.

    • Diagnostic testing is performed to make or confirm a diagnosis of a specific disorder in a person who generally already has signs or symptoms of that disorder.

    • Predictive or presymptomatictesting is performed on a person who generally has no signs or symptoms of a specific disorder at the time of testing, in order to determine whether or not that person has genetic variations that increase the likelihood that the person may, or will, develop the disorder in the future. Predictive testing is often performed in relation to genetic disorders that are not evident at birth but have their onset during adulthood. Predictive testing is also called presymptomatic testing where an individual’s family medical history suggests that he or she may have the genetic disorder but symptoms of it are not yet manifest.

    • Genetic carrier testingis performed on a person to determine whether or not that person has a genetic or chromosomal abnormality that does not generally affect the person’s health but increases his or her chance of having children with the disorder in question.[5] The outcome of such testing can influence future reproductive decisions.

    • Screening testing is performed on people who are not necessarily known to be at increased risk of a particular genetic disorder. Screening tests can be conducted on individuals, groups and entire populations, such as with postnatal screening using newborn screening cards. Cascade screening is a form of screening where once an affected individual is identified, potentially affected relatives are systematically identified and offered testing. In some cases screening testing is an extension of genetic carrier testing since it allows asymptomatic individuals in the community to be tested to see if they carry a genetic variation or mutation. This information may be helpful in family planning or in facilitating preventive measures to avoid disease.[6]

    • Pre-implantation and prenatal testingis performed on a foetus in utero (or pre-implantation in the case of embryos used in artificial reproductive technology procedures). Prenatal genetic testing is typically performed where there are ‘at risk’ parents, such as parents who are carriers of mutated alleles for cystic fibrosis, Tay-Sachs disease, or b-thalassemia. In the longer term, early detection through prenatal diagnosis may permit use of therapies such as blood transfusion, surgical correction or, possibly, gene therapy.

    • Research testinginvolves the systematic analysis of genetic information to advance medical or scientific knowledge about how genes influence the health of individuals and populations. Genetic research testing may be conducted on identified or de-identified samples and generally requires the approval of a Human Research Ethics Committee, which oversee issues of consent and other ethical concerns.[7]

    • Identification testing or forensic testingis currently performed on non-coding DNA, with respect to a number of agreed core loci, to construct a DNA profile. This profile is then matched against the profile from another DNA sample, for example, from a crime scene. This identification process is used in criminal investigations to exclude or identify a suspect, in searches for missing persons, and in the identification of deceased persons.[8]

    • Parentage and other kinship testing is performed to determine whether two people are biologically related to each other. Parentage testing is the most common form of kinship testing and may be done for various purposes, including in relation to family law proceedings, immigration applications and disaster victim identification.[9]

[5] Individuals sometimes experience mild health effects as a result of being carriers of the relevant mutation.

[6] For example, the knowledge that someone carried the genetic defect for haemochromatosis might allow the relatively simple option of blood letting to prevent complications from the condition.

[7] See Pt D.

[8] See Pt J.

[9] See Ch 35–37, 42.