Hint: Look for links to other sources of information, e.g. references in the text, websites, other literature, telephone numbers, postal addresses, help lines, support groups, other health professionals.
A good quality publication will describe the risk of developing, carrying or passing on a genetic condition in a way that is easy to understand. It is important that the publication enables you to understand clearly why you might or might not be at risk, and what your risk (chances or likelihood) of different outcomes might be. The explanation should help you to understand why testing might or might not be recommended for you and what it may reveal about the type and level of risk you may confront.
The question focuses on the risks of developing, carrying or passing on a genetic condition, and not risks associated with the test procedure (Question 7), test accuracy (Question 8), or treatment choices (Question 4). This question is only concerned with the risk or risks described in the publication and cannot be used to tell you whether all of the risks have been described, as this would involve checking against other sources.
Risk information is based on studies of disease patterns in large groups of people with the genetic condition and in the general population. An individual's risk is an estimate of the chance or probability or likelihood of a particular outcome, and is often described using statistics such as 1 in 100, 1%, and so on. An important part of explaining these risks is also acknowledging uncertainty where aspects of the condition and its development are poorly understood.
You may find it helpful to consider 2 main issues when rating this question - (i) the risks involved and (ii) the way the risk is explained. Terms used below are described fully in 'Background to genetic screening and testing' and Glossary.
(a) Do I have the faulty gene? Will I pass it on?
Information about who the mutation and condition affects is important for understanding your risk. You may be at greater risk for a condition with a genetic cause compared with other people in the general population because the condition runs in your family. This may be linked to your ethnicity or geographical roots - there may be a higher rate of carriers or people with the condition in families from your background than in families from other ethnic groups.
Risk may not be related to family history but to other factors such as your age (e.g. the chance of having a child with Down's Syndrome) or unpredictable individual circumstances (e.g. a new, sporadic mutation). Here, a description of how the mutation and condition may arise and the reasons why you may be at risk are important. The random nature and lack of scientific knowledge surrounding some of these events should also be described honestly.
If a condition with a genetic cause runs in your family, there is a chance you have inherited the mutation and will pass it on to your children. You may be affected yourself or you may be an unaffected carrier. To understand risks here, you need information about patterns of inheritance and the likelihood or chance of individual family members having or not having the mutation (e.g. "if both partners carry the faulty gene, then your child has a 1 in 4 chance of inheriting this gene - so a 3 in 4 chance of not inheriting it"). This can also be presented in diagram form as a family tree or pedigree using symbols for different types of risks and relationships (e.g. affected and unaffected siblings; carriers; types of twins etc). We have included an example in the Background and in Example (iii) below.
Risk information presented this way can help you understand your own risks and those of your relatives, and can clarify the possible reasons for testing and likely outcomes of testing.
The chances that an asymptomatic individual with a mutation will go on to develop disease varies with each condition. For some diseases, everyone who has the mutation will develop the disease (e.g. Huntington's disease). A positive predictive test result in such cases means you will certainly develop symptoms at some stage. For many other conditions, a result indicating you have a mutation does not necessarily mean you will develop symptoms or the condition, and even a confirmed diagnosis can be associated with different outcomes. If you are a carrier for a recessive disorder, you may not be affected by the condition, but it is possible that one or more of your offspring will be. The publication should link information about symptoms and disease progression with the likelihood of these outcomes in individuals with the mutation.
Information about the risk of developing symptoms or a condition is often described as a "life-time" risk. For example, if your lifetime risk is 70%, it means that 7 out of 10 people with this genetic mutation develop the condition at some point in their lives. See the references resources in Part 6 for more information about lifetime risk estimates.
Many screening tests in pregnancy and at birth provide useful information about risks that may need further investigation. Genetic screening tests commonly offered in pregnancy (e.g. cystic fibrosis) and at birth (e.g. sickle cell disease) may indicate that a baby is at increased risk, but a further diagnostic test would be needed to confirm or reject this result. A publication should provide an explanation of risk arising from each of these stages.
Understanding risk can be difficult, as it often involves imagining and comparing possible outcomes in the future with no certainty about what will happen to you. Our reactions to different types of risk estimates and ways of explaining them can also be unpredictable.
There has been a lot of research in recent years into ways of explaining risk. Ideally, the risk estimates and language most meaningful to you should be agreed within the consultation. However, information can also be helpful to you and a wide range of other users if it follows some good practice principles. The hints accompanying Question 5 in the DISCERN Genetics tool outline some suggestions.
Guidelines for rating the question
The information needed to rate this question can be very detailed and will usually be provided with information about the condition (Question 3) and the nature of the test (Question 6). We have devised simple examples here to demonstrate the quality criterion underlying Question 5. However, the information rated by this question should also have clear sources and referencing where appropriate as outlined in Question 16. The sources of the real data used in the examples below are provided in Part 6. For further guidance and general examples of referencing, please refer to Question 16
A family doctor's website provides the following information in a section about a new genetic test for a cancer that has received a lot of media coverage:
This cancer is not common, affecting approximately one in every 10,000 people - so it would probably only affect 1 person from our small town. Most cases (9 out of 10 or 90%) develop as a result of chance and the reasons are not yet clearly understood. Fewer than 1 of every 10 cases of this form of cancer (less than 10% of cases) are thought to be inherited. You would therefore need to discuss your family history and health with your doctor to assess your risk before testing could be recommended. If testing shows you have inherited the mutation for this cancer, you will not necessarily develop the disease - 6 in 10 (60%) people with the mutation develop symptoms (so 4 in 10 don't), which usually happens by the age 50.
An international charity leaflet provides the following details about inheritance of Huntington's disease:
Huntington's disease is an autosomal dominant genetic condition, which means you only need to inherit the faulty gene from one of your parents to get the disease. So, if you have a parent with Huntington's disease, you have a 50:50 chance of inheriting and an equal chance of not inheriting the faulty gene. If you have inherited the gene, each of your offspring will also have the same risk. Males and females are affected equally. Everyone who inherits the faulty gene will, at some point, develop the disease. Unfortunately, because it is a late onset disorder, you may not know you are at risk until you have had children and passed on the condition. Support and counselling for you and your family is therefore an important part of the test procedure.
The patient information section of a hospital genetics department website provides the following information about Tay Sachs disease:
Tay Sachs Disease is an inherited neurodegenerative disorder. It usually begins in infancy. There is no treatment or cure, and affected infants usually die before age 5 (cases of later onset usually die by the age of 15).
Tay Sachs occurs most frequently in people with Ashkenazi Jewish ancestry (descended from the Jewish populations of Central and Eastern Europe). The disease is approximately 100 times more common in infants of Ashkenazi Jewish ancestry (about 1 per 3,000 births) than in other infants (about 1 in 300,000 births in other ethnic groups). Each sex is equally affected.
Tay Sachs is a recessive disorder, which means that both parents have to be carriers to pass on the faulty gene. 1 in 30 people with Ashkenazi Jewish ancestry are carriers for Tay Sachs, and if you and your partner share this background, there is a 1 in 900 chance that you are both carriers and risk passing the condition on to your children. Each pregnancy will have 4 possible outcomes: a 25 in 100 chance that the baby will have the disease, a 50 in 100 chance that the child will be a carrier, and a 25 in 100 chance that the child has not inherited the faulty gene. The following diagram shows how the condition runs in families:
6.1 Autosomal recessive conditions: Both parents are carriers, 'a' is the gene with the recessive mutation. Example: Cystic fibrosis
Access to a national screening programme is available through this hospital for all young adults and pregnant women from this background.
A UK obstetrics department leaflet provides the following explanation of risk estimates arising from a screening test for Down's Syndrome:
The risk of having a baby with Down's syndrome increases with the mother's age. It is not clear why this happens, although it is likely that chromosome abnormalities occurring during the formation of the egg prior to conception become more common as women get older.
The screening test for Down's syndrome provides a clearer estimate that your baby might be at risk than your age alone. It involves taking a sample of your blood and conducting biochemical tests. If your baby has Down's syndrome, you will have raised levels of some biochemical markers for Down's syndrome in your blood. This information is combined with information about your age and stage of pregnancy to produce a numerical estimate of risk for Down's Syndrome . A cut-off risk estimate of 1 in 250 is usually used, and results above this figure are described as "screen positive". If your results come back with a figure over 1 in 250, this does not mean that your baby definitely has Down's Syndrome. It means that 1 person with this result will have an affected baby, but about 249 people will not. There is therefore a 1 in 250 chance (about 4 in 1000 or 0.4%) that your baby may be affected and you will be offered a more accurate test (see the following section) to confirm how likely this is.
If your risk is less than 1 in 250, you will be described as "screen negative". This level of risk is interpreted as meaning you are very unlikely to be carrying a baby with Down's Syndrome although it does not mean your risk is zero: for example, a risk of 1 in 500 this still means that 1 in 500 pregnancies with this result will carry a baby with Down's syndrome). Because there are risks associated with further diagnostic testing, we do not recommend it for women with this low level of risk.
Our healthcare team are here to support you and will be happy to discuss the screening tests, results and options with you in more detail.
Details of the diagnostic test procedures are then provided.
A family medical health reference book includes the following background in a section on sex-linked disorders and genetic testing:
This is an inherited degenerative disorder, and symptoms usually develop in adult life. However, there is a probability that some children born with this condition will develop very severe physical disability at an early age, but it is not currently possible to predict who this might be or when this will happen.
Additional rating notes: there is no description of inheritance patterns or clarification of the terms "usually" or "probability" or "some children". However, the reference to uncertainty is a positive feature.
An article on breast cancer in a women's magazine contains the following:
If there is a history of breast cancer in your family, you may also be at risk. You should discuss this with your doctor and investigate options for genetic testing.
Additional rating notes: the nature of the family history is unclear, and the link between family history and genetics is not explained. The size and nature of the risk is not specified.
A maternity hospital leaflet provides information for parents on neonatal screening. It includes a brief description of the conditions being detected and the test procedure, which is a blood spot test. The conditions are described as rare but there is no information on prevalence or incidence. Some conditions are also described as inherited with no further explanation of how they are passed on, or whether the parents, older children or future pregnancies would also be affected if the test is positive. Screening is described as aiming to detect babies more likely to have these conditions, and results are described as either indicating your baby is normal, or thought to have a condition which may require further action. The possibility that a baby may be found to be a carrier for a condition is also mentioned without any explanation of this term. No further information or statistics are provided on each stage of testing.
Additional rating notes: the risk language and descriptions are too general, brief and imprecise to give parents meaningful information for understanding risks and for making an informed choice about genetic testing.
A commercial online health encyclopedia has the following entry for a genetic condition and testing:
This is an inherited disorder. People with this condition have numerous symptoms (described) and reduced life span. A number of tests, including DNA testing, are used to detect the condition.
Additional rating notes: There is no mention of any risk or chance associated with any aspect of the disorder or testing.