Diagnostic testing is the situation where an individual is suspected of having a particular condition and a specific gene/s is/are tested to look for disease causing mutations. This can confirm the clinical diagnosis for the patient.

Genetic testing holds great potential for the future of medical care. It offers many benefits, including providing important information that can be used when making decisions about having a family and taking care of one’s own health. However, there are also limitations. For this reason, it is important to understand the nature of genetic testing and the information that it can and can’t provide. For example:

  • Predictive tests will not determine if an individual has a disease causing mutation or variant which may, at a later date, cause a particular genetic condition. Such results are not definitive and may leave a person wondering what to do with those results, particularly as one cannot usually predict the timing of disease onset or the severity of the condition. Predictive testing should usually be done by a clinical geneticist or a genetic counsellor familiar with the disease.

  • A particular genetic test will only provide information about the specific gene/disease being tested for. It does not provide information about other genetic diseases not being specifically looked for by that test.

  • While the test may detect a particular problem gene, it cannot predict how severely the person carrying that gene will be affected. For example, with cystic fibrosis, symptoms may range from mild bronchial abnormalities to severe lung, pancreatic, and intestinal problems.

  • Many genetic tests cannot detect all of the variations that can cause a particular disease. For instance, with genetic testing for cystic fibrosis, most genetic testing panels only look for the more common variants, not all of those that are associated with this disease. So, not finding a gene alteration may not exclude the condition; this needs to be decided from a clinical basis.

  • Many diseases are the result of an interaction between one’s genes and one’s environment. The way in which these interactions cause disease is not clearly understood. Examples of these diseases include coronary heart disease, type 2 diabetes, obesity, and Alzheimer disease.

  • Legal issues, such as patient privacy, use of genetic testing to determine insurance coverage, and the use of archived patient samples are some of the broader social issues to be considered.

It is important to remember that genetic testing is different from other types of laboratory testing. Results of genetic tests may have implications not only for the patient, but also for the family members who may need to be tested as well. In addition, genetic education and counselling is often advised to help understand and cope with the results of genetic tests.