Hint: Look for an explanation on the type of tests available or being offered. Is the test being done
A good quality publication will provide clear information about the type of test available and its purpose.
Such information will highlight what you can and cannot find out from being tested. This information can help you make an informed choice about testing by clarifying what the test is for, why it is being done and what the consequences might be. These details may help you decide whether testing is appropriate for you. It is important to remember that a blood or tissue sample may be obtained for a variety of tests, in some cases this may be for a genetic test and in other cases it may be for another type of test.
A full description of the nature of genetic tests is outlined in the background section 'genetic screening and testing' and the Glossary. Rate this question according to whether it provides clear information about the nature of the test, including the reasons for testing and the type of test available. Note that this question is not about the actual testing procedure (Question 7) or the accuracy of the test (Question 8).
Guidelines for rating the question:
We have devised simple examples here to demonstrate the quality criterion underlying Question 6. However, the information rated by this question should also have clear sources and referencing where appropriate as outlined in Question 16. For further guidance and examples, please refer to the section on Question 16
A hospital neurology department patient handout provides the following background to genetic testing for Huntington's Disease (a separate section outlines details of the test procedure, including an explanation of the genetic mutation and test accuracy):
Testing is done in a laboratory on DNA taken from your blood sample. The test is to find out whether or not you have inherited the faulty gene that causes Huntington's disease.
This test is being offered to you for one of the following reasons:
i. you have a family history of Huntington's and you may also be affected - even if you are not showing any signs or symptoms at present
ii. you are experiencing symptoms which suggest that you may have Huntington's disease and a test is needed to confirm (or reject) this diagnosis.
A clinical genetics department website provides the following information about testing for an X-linked disorder:
The pattern of inheritance for this condition is called X-linked recessive. This means that the genetic fault responsible for this condition is carried by females but only male offspring develop the condition. This is because females carry 2 copies of the X sex chromosome and one will therefore function normally. Males only have one X chromosome and so if this is faulty, they will show the disease.
We offer 2 types of genetic test to families affected by this condition. Female family members can be tested to estimate the likelihood that they are carriers of the mutation. Tests can also be done during pregnancy to find out whether the foetus is affected. In both types of test, we send a small sample of blood to the laboratory where it will be analysed for the genetic fault which causes this condition.
The accuracy of these tests and the interpretion of results are then discussed in detail.
A UK hospital obstetrics department leaflet entitled Diagnostic Tests for Down's Syndrome provides the following information:
You are being offered further tests in your pregnancy because you have received a "screen-positive" result for Down's Syndrome from your screening test. This result means there is at least a 1 in 250 chance ( 0.4%) that your baby is affected, and a diagnostic test is recommended if you want more precise information about your risk There are 2 diagnostic tests available at this hospital - amniocentesis and chorionic villus sampling (CVS). These tests involve taking a sample of material that contains genetic information from the fetus (either amniotic fluid or placental tissue) and examining it in the laboratory for evidence of the chromosome abnormality that causes Down's syndrome.
Full details of each of these test procedures, accuracy and issues to consider before testing are described later in the leaflet.
A Web page produced by a disability self-help group includes a section on an inherited muscle disorder. The main focus of the page is a description of the symptoms, treatments and support available for those affected. There is a brief section on inheritance patterns which concludes Recent research breakthroughs have ensured that a genetic test is now available for those that need it.
Additional rating notes: The nature of the test has to be inferred from information about inheritance - there is no clear description of what the test detects or who it is meant for.
A maternity hospital leaflet for parents provides information 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. The term screening is used but is not defined and is described as aiming to detect babies more likely to have these conditions. Screening 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 reasons for testing are unclear due to a lack of discussion about risk (prevalence, inheritance factors) and no clear description of "screening". There is no distinction between genetic testing and other forms of test performed on the blood sample. There is no clear explanation of what the screening results mean, particularly if not "normal", and no clear reference to the possibility of further testing if a result is "abnormal" and requires action.
A University hospital web page entitled Haemochromatosis provides detailed information about the genetic mutation underlying the condition and the technicalities of the genetic test. Although the condition is described as inherited, no other context for testing is given.
Additional rating notes: There is no indication of who the test is for or what the results are meant to indicate.