The other major genetic causes of venous thrombosis (deficiencies of protein C and S) together account for only 5-10% of cases.
Factor V Leiden increases the risk of venous thrombosis 3-8 times for heterozygous (one bad gene inherited) and substantially more, 30-140 times for homozygous (two bad gene inherited) individuals.
2% of the general population was found to be heterozygous.
Risk is increased still further in situations such as pregnancy, oral contraceptive use, estrogen therapy, malignancy, diabetes mellitus, immobilization, surgery, trauma, high blood pressure, obesity, smoking or long time travel (commonly called economy class syndrome). In these cases risk of clotting can increase dramatically.
Can Factor V Leiden be inherited?
Genetic mutations are passed from generation to generation. This is because we receive our DNA from our parents.
Our genetic information is inherited in pairs. Every gene has two copies, one from our mothers and one from our fathers. Different conditions can be inherited in different ways. In terms of Factor V Leiden, only one of a person's two copies of a gene must have a mutation in order for that individual to have an increased risk of clotting. This is called dominant inheritance.
If a person is homozygous, (both mutated gene) they are at a greater risk to develop a blood clot than an individual who is heterozygous.
An individual will also have a greater risk to develop a blood clot if they inherit a mutation in more than one gene that leads to thrombophilia. For example, a person has a greater risk to develop a blood clot if they have factor V Leiden and prothrombin.
Then what is the chance of passing on?
To predict the risk, a few factors must be considered.
The first is whether or not you are heterozygous or homozygous for the gene. As stated above genetic test can tell you whether or not you are heterozygous or homozygous.
If one of the parents is heterozygous for the gene mutation, there is a 50:50 chance that their offspring will inherit the gene mutation. This is because there is an equal likelihood that they will pass on the gene copy with the mutation OR the gene copy that is normal. Which copy of the gene their offspring will inherit is a chance event. There is nothing an individual can do to alter this chance.
If one of them was homozygous for the gene mutation, their child will definitely inherit it. This is because they do not have a normal copy of the gene, and it is therefore impossible to pass on a normal copy to your child.
Because of all the danger of Factor V Leiden, test is necessary especially for those who already suffered venous thrombosis, has a family history of the disease etc…
Some of the tests are simple blood test, which checks the aPTT (the speed of clot) and if the patient were found positive in the venous thrombosis they go through the molecular testing.
The test analysis the mutation of the factor v gene looking at whether the FV gene is showing resistance to the protein c or not, and if so they go through a further test to find out whether the patient is homozygous or heterozygous. The accuracy of the test is almost 100 %.
The proposal of Mr. Clotter is disagreed because of some of these reasons:
Economically the test is too much of a loss than the gain.
There are several screening tests for Factor V Leiden. The molecular genetic testing for the factor V Leiden mutation is most common and accurate. The overall cost to test one person is about 85~100 dollar, making it quiet cost efficient.
Unfortunately, Factor V Leiden cannot be cured. Therefore the aim of the screening would be to reduce the chance of Factor V Leiden carrier from getting DVT or pulmonary embolism and most importantly to reduce the mortality through advices and making the person aware of what disease they have. Advices include the ban of the factor that may increase the risk of DVT, such as oral contraceptives or airline travel.
However, yet there has been no studies done that provides sufficient evidence that advices will help to reduce the percentage of FVL carriers from getting DVT.
Also according to the survey only 3% of the general population are Factor V mutation carriers and none of the Australasian was found to be homozygous.
"Normal" people have a 1 in 1000 chance of thrombophilia and a person with the mutation have only 3~8 in 1000 chance of thrombophilia, which is not very significant compared to the normal gene carriers. Use of oral contraceptives can increases the risk dramatically up to 30 in 1000.
However the disease thrombophilia was found out to be not particularly life threatening unless it develops Pulmonary embolism which only occurs in 20% of the all DVT patients.
If this is the case, does it worth testing on all of the country’s high school female students spending millions of dollars, just to grab 3% of those who only have 8 in 1000 chance of getting DVT which is not a deadly disease and also when it is still uncertain whether the testing will be beneficial or not?
Not only economically but also socially and ethically the testing is wrong.
In every medical ethics there are 5 fundamental questions that needs to be answered, 1) is it beneficial?
2) does it harm? 3) is it fair? 4) does it respect for the autonomy of a patient? and lastly 5) does it do benefit for the majority?
Screening can be beneficial, it informs the patient of what disease they have and how to prevent it from developing in to DVT or PE. However as shown above there has been no proved research that advices will do any benefit to the individual. Most importantly there is also much harm that can be done by suggesting them the ban of the risk factors. It restricts their life and causes deterioration in mental and social well being.
First of all it will cause an unnecessary anxiety. They will always be depressed and scared that they might develop DVT or PE. They will be very anxious of all the movement they make.
This anxiety causes deterioration in mental health causing enormous stress.
Secondly everyday life will be restricted, restriction involve lose of right to use oral contraceptives, lose of right to do some things they like such as to travel overseas with their family, therefore the life of all family members will also be restricted.
Lastly the social discrimination towards the mutation carriers.
They will not be able to get jobs that require sitting down for long time such as pilots or any jobs flying and most importantly they will not be able to get medical insurance, because insurance companies put profit before the rights of people.
Screening can be very useful, but no research was made to prove the benefit and the maleficent side effects over weighed the benefits.
There are some of benefit proven screenings such as breast cancer screening or hip replacements for the elderly, which will provide benefit for the individual society and the majority.
The country should therefore spend more money on the proven screening rather than the unproven ones like the Factor V Leiden screening.
Factor V Leiden is a mutation that occurs in the Factor V gene which is a clotting factor. When mutated it is not destroyed by Protein C or S causing a unnecessary clot in our body.
I disagree with screening for the mutation for all 16 year old high school girls, because there are no direct evidence to support the introduction of screening high school students for Factor V Leiden.
Potential benefits are reduction of chance of DVT while some dis-benefits are restriction in life, deterioration in mental and social health.
In conclusion, dis- benefit tended to overweigh the benefit of the screening.
I believe the screening should be carried out only on those who are mostly likely to have Factor V mutation, among these people are people with DVT family history and people who have suffered DVT previously.
RESOURCES
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8)
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10)
11) http://www.hta.nhsweb.nhs.uk/rapidhta/publications/DEC58.pdf
12) http://www.aic.cuhk.edu.hk/web8/pulmonary_embolus_and_dvt.htm
13) http://circ.ahajournals.org/cgi/content/full/107/15/e94
14)
15) http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Deep_Vein_Thrombosis.html
16) Journal Watch Women's Health 1998 Jan 1
17) The Lancet, Volume 347, Issue 9012, 18 May 1996, Pages 1346-1347 Björn Dahlbäck
ENTRY FORM: GENETHICS 2004 COMPETITION
Student Details:
Name of student: John Ko (Kyung-Hwan Ko)
Date of Birth: 17/12/1987 16 yrs old.
Currently studying NCEA Level 2 (English, History Chemistry) Level 3 (Calculus, Physics)
Student address: Flat 9/315 Worcester Street, Linwood, Christchurch, New Zealand.
Email: [email protected]
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Name of the School: St Bede’s College.
School address: P.O BOX 5380, 210 Main North Road, Redwood, Christchurch 8005,
New Zealand.
Telephone: (03) 352-6065 Facsimile: (03) 352-0345
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Name of Teacher in charge: Dr Catherine Owens y de Novoa
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I had to ask Peter Spratt forthe requirements.
