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Discern Genetics Quality Criteria

Question 15

Does it provide details of additional sources of support and information?

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.

Guidance for question 7

What the question is about and why it is important

A good quality publication will provide details of the testing procedure. Information about all aspects of the testing procedure is important when deciding whether or not to be tested. It helps you to understand what testing involves and what to expect during testing.

Testing procedures for genetic conditions can vary according to the nature of the test (see Question 6) and the way health services are organised. For example, some are quick, simple and painless procedures, whereas others may involve some physical discomfort, or are associated with additional risks. Some are conducted through local primary care or family medicine services, whereas others may only be available through hospitals or specialist centres. Some are publicly available whereas others involve payment or private care. Most involve counselling before and after testing, but how and where this is done and the time taken to receive results may vary. The decision-making process itself can prove stressful and time-consuming, regardless of whether the actual procedure is simple or complex.

Rating the question

Rate the question according to whether it provides a clear description of the testing procedure.

Guidelines for rating the question:

  • 5: yes - the publication provides clear information about the testing procedure
  • 2 - 4: partially - the testing procedure is described, but the information is unclear or incomplete
  • 1: no - there is no information on the testing procedure

Examples

We have devised simple examples here to demonstrate the quality criterion underlying Question 7. 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

5 Rating:
Example (i) Inherited cancer

A national cancer charity website provides the following information on a genetic test for cancer:

Background to testing

Genetic testing is only recommended for people with a strong family history of this form of cancer. The probability that you have the genetic mutation is first assessed by examining your family history - this is usually done during a consultation with your family doctor. If you are at risk, you will be offered a referral to a special clinic for testing. The test is only available free at certain clinics. Your doctor can provide you with information about the different providers, test availability and test performance.

The test procedure

Going to the clinic does not mean you are obliged to take the test. You will meet with a counsellor who will discuss all aspects of this condition and testing procedure with you. All clinics offering this testing procedure free to the public follow agreed guidelines which means that the counselling is spread over several sessions to give you time to decide, and you can withdraw from the procedure at any time.

If you decide to have the test done, a nurse at the clinic will take two separate blood samples. The samples are then sent straight to the hospital laboratory where DNA is extracted and analysed. Two samples are tested to enable laboratory staff to check the results.

The blood test itself is very quick and is similar to having an injection, so you should not experience any discomfort. Following the test the counsellor at the clinic will support you and keep you informed, and will contact you for an appointment and further counselling when your results become available.

Example (ii) Antenatal testing - Down's syndrome (based on real statistics - see Question 16 Example (i))

A government health department website has a section on diagnostic tests in pregnancy. It includes the following information about the amniocentesis procedure for detecting Down's syndrome:

Amniocentesis is a diagnostic test which can confirm whether your baby has Down's syndrome. It can also detect a number of other genetic and congenital conditions described elsewhere on this website. It is available free in all health regions to all pregnant women who receive a positive screening test result, are aged over 35, or have other risk factors.

The liquid in the womb is called amniotic fluid. It contains cells from the fetus which carry its genetic information (DNA on chromosomes). Amniocentesis is performed by an obstetrician at your local hospital at around the 15th week of pregnancy and involves extracting a sample of amniotic fluid and sending it to the hospital laboratory for testing. In the laboratory test, the chromosomes in the baby's cells are identified and counted (this is a cytogenetic technique). If your baby has Down's syndrome, it will have an extra copy of chromosome 21.

On the day of the test, you will need to arrive at the hospital with an empty bladder, and it may be helpful to have arranged for someone to drive you home and spend time with you afterwards. The doctor uses ultrasound to guide a hollow needle through your abdomen to take a small sample of the amniotic fluid surrounding your baby. You should only feel slight discomfort, and some hospitals offer an injection with a local anaesthetic. The procedure only takes a few minutes but before leaving the hospital, your baby's heartbeat will be checked and you will be asked to stay for an hour's observation. You should then go home and rest for the day. A cramping feeling afterwards is normal, but you should contact the hospital if you start to leak blood or fluid from the vagina.

If you have a rhesus negative blood group, the procedure may cause rhesus positive blood cells from your baby to enter your blood stream and your body may develop antibodies which could harm the baby. You will be given an injection into the muscle of your arm or leg after the test to prevent the antibodies developing Full details of this treatment are provided in another section (link to another section of the site).

Results

Additional cells are usually grown from the amniotic sample to provide enough material for the laboratory analysis. The growth of these cell cultures can take several weeks. A preliminary result may be available within 48 hours but a firm result will not be available for two to three weeks. In a small number of cases, the culture growth fails and the test may need to be repeated.

Risks and Disadvantages

Amniocentesis during the second trimester of pregnancy is associated with a slightly increased risk of miscarriage (approximately 1% or 1 in 100 amniocentesis procedures are associated with miscarriage). This risk is higher earlier in pregnancy which is why amniocentesis is not usually offered before 15 weeks. When deciding about having amniocentesis, you therefore need to balance the advantages of having information about the baby's chromosomes against the small risk of losing the pregnancy.

The timing of the test during the second trimester and the waiting time for test results also means that if your results are positive, you may be making decisions about a termination at a fairly advanced stage of pregnancy. You will have opportunity to discuss the procedure and any concerns you have with your obstetrician and healthcare team before the test.

Additional issues

In some cases, such as multiple pregnancies or HIV positive mothers, amniocentesis may present additional risks or may not be possible. Your healthcare team will discuss your options with you.

Before deciding whether to have an amniocentesis test, you might like to compare this information with the benefits and risks of another diagnostic test - chorionic villus sampling ).

Partially rating:
Example (iii) Antenatal screening - Cystic Fibrosis

The procedure simply involves you and your partner providing a mouthwash sample early in your pregnancy. The sample is sent to a local hospital laboratory for analysis. If the results come back positive, you will be called back for further testing.

Additional rating notes: There are no details of when, where, or how the sample is provided or who collects it, what the test results are based on, or waiting time for results.

Example (iv) General example

Testing is available to determine whether or not a person has inherited the genetic mutation that causes this condition. The testing can be done on a blood or tissue sample, and usually takes between 2 to 4 weeks for results.

Additional rating notes: There are no details of where or how the sample is provided or what the test results are based on.

1 rating:
Example (v) Cancer example

A hospital Web page entitled Genetic testing for breast cancer describes a genetic mutation linked to breast cancer and the risks associated with having this mutation. It mentions a simple test for detecting mutations in these genes, and describes in detail the consequences of a positive result.

Additional rating notes: There is no information on the actual testing procedure.