Releases Saturday 28 April 2001
No 7293 Volume 322

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(1) FAMILY HISTORY IS A POOR PREDICTOR OF
VENOUS CLOTTING

(2) PREDICTIVE GENETIC TESTS RANGE FROM HIGHLY
USEFUL TO POTENTIALLY HARMFUL

(3) WOULD KNOWING YOUR GENETIC RISK CHANGE
YOUR BEHAVIOUR?

(4) GENES AND ENVIRONMENT IMPORTANT IN
FAMILIES WITH HISTORY OF HIGH CHOLESTEROL

(5) PRIMARY CARE PRACTITIONERS NEED TO BECOME
GENETICALLY LITERATE



(1) FAMILY HISTORY IS A POOR PREDICTOR OF
VENOUS CLOTTING

(Value of family history in identifying women at risk of venous
thromboembolism during oral contraception: observational study)
http://bmj.com/cgi/content/full/322/7293/1024

Family history of venous thromboembolism (blood clotting) is an
unsatisfactory predictor for identifying common thrombophilic
defects in women without thrombosis before taking oral
contraceptives, finds a study in this week's BMJ.

A total of 324 women (mean age 34 years) with no personal
history of venous thromboembolism were screened for common
inherited thrombophilic defects before taking oral contraceptives.
Before screening, the women were surveyed to evaluate both
personal and family history of venous thromboembolism. A
family history was considered positive if a thromboembolism was
reported in any first or second degree relatives.

The proportion of women with thrombophilia was similar among
those with a positive history and those with a negative history of
venous thromboembolism when both first and second degree
family history was considered.

These findings suggest that family history of venous
thromboembolism is an unsatisfactory predictor for identifying
carriers of common thrombophilic defects before taking oral
contraceptives. A policy of selective screening may therefore
miss a substantial number of women at increased risk of
thromboembolism when taking oral contraceptives, conclude the
authors.

Contact:

Benilde Cosmi, Lecturer, Cardiovascular Department, Division
of Angiology, S. Orsola-Malpighi University Hospital, Bologna,
Italy
Email: bcosmi@med.unibo.it

(2) PREDICTIVE GENETIC TESTS RANGE FROM HIGHLY
USEFUL TO POTENTIALLY HARMFUL

(The complexities of predictive genetic testing)
http://bmj.com/cgi/content/full/322/7293/1052

Predictive genetic testing has the potential to save lives through
targeted surveillance and preventive measures, but a paper in this
week's BMJ reports that most genetic tests carry a degree of
uncertainty, which limits their usefulness and, in some cases, can
even be harmful to patients.

For some diseases, predictive genetic testing is highly useful. For
example, testing for multiple endocrine neoplasma type 2 - a rare
disorder leading to thyroid cancer - makes it possible to identify
those who will benefit from preventive surgery. For other
conditions, such as breast and ovarian cancer, genetic testing can
be useful to identify those at increased risk, but utility is limited
because of considerable uncertainty about the predictive value of
the test. The benefit of testing is further limited by the nature of
available surveillance and prevention strategies for these
conditions.

Alzheimer's disease illustrates the potential for predictive genetic
testing to cause harm. A positive test is an imprecise measure of
risk and could result in anxiety, stigmatisation, or discrimination.
Currently such testing would generally be unethical because no
effective prevention is available.

Such tests will be increasingly available as the genetic factors that
underpin common diseases are identified, say the authors.
However, predictive testing must be tailored to the individual's
needs and preferences, they conclude.

Contact:

James P Evans, Director of Cancer Genetics Services,
Department of Medicine and Lineberger Comprehensive Cancer
Center, University of North Carolina, USA
Email: jpevans@med.unc.edu

(3) WOULD KNOWING YOUR GENETIC RISK CHANGE
YOUR BEHAVIOUR?

(Genetic risk and behavioural change)
http://bmj.com/cgi/content/full/322/7293/1056

Providing people with genetic information on risk
may not increase their motivation to change behaviour, and in
some cases may decrease motivation, finds a review in this
week's BMJ.

Using the limited evidence and the literature on behavioural
change, the research team examined if and how people's
behaviour might be changed when given DNA based information
about their chances of developing potentially preventable
diseases such as heart disease and cancer.

The current evidence suggests that providing people with DNA
derived information about risks to their health does not increase
motivation to change behaviour beyond that achieved with
non-genetic information, report the authors. For instance, since
the introduction of predictive genetic testing for risk of breast
cancer, no significant changes in screening behaviour have been
found.

For some people, genetic information may even reduce
motivation to change behaviour, add the authors. For example,
parents who tested positive for high cholesterol levels led to a
sense of fatalism, based on the belief that genetically conferred
risks are serious and immutable.

Further research is needed to evaluate programmes in which
genetic risk information is given, including evaluation of different
ways of giving information, they conclude.

Contact:

Theresa Marteau, Professor of Health Psychology, Psychology
and Genetics Research Group, King's College London, UK
Email: theresa.marteau@kcl.ac.uk

(4) GENES AND ENVIRONMENT IMPORTANT IN
FAMILIES WITH HISTORY OF HIGH CHOLESTEROL

(Mortality over two centuries in large pedigree with familial
hypercholesterolaemia: family tree mortality study)
http://bmj.com/cgi/content/full/322/7293/1019

Risk of death varies significantly among patients with a family
history of high cholesterol (familial hypercholesterolaemia), with
many untreated patients reaching a normal life span, finds a study
in this week's BMJ.

This suggests that strong interactions between genetic and
environmental factors are involved in this disorder, and
emphasises how much we still have to learn about the relation
between genes and the environment.

Using official records of births, marriages, and deaths,
researchers in the Netherlands examined mortality over two
centuries in a large family with a history of high cholesterol. They
found that the excess mortality from this disorder varied over
time. For instance, in the 19th and early 20th century, mortality
was lower than in the general population. It rose after 1915,
reached its maximum during the 1950s, and fell thereafter.
During the decades with excess mortality, survival ranged from
normal life expectancy to severe excess mortality in different
branches of the family tree.

This large variation of risk suggests that previous studies, with
families based on selected patients, may have overestimated
mortality, say the authors. Moreover, such large variation in
mortality in two directions (over time and within generations) in a
family indicates that the disorder has strong interactions with
environmental factors.

Future research is required to identify patients who are at
extreme risk of premature death, and which environmental
factors are effective in modulating this risk, conclude the authors.

Contact:

Eric J G Sijbrands, Department of Vascular Medicine and
General Internal Medicine, Academic Medical Centre,
Amsterdam, Netherlands
Email: nrexpert@euronet.nl

(5) PRIMARY CARE PRACTITIONERS NEED TO BECOME
GENETICALLY LITERATE

(The challenge of integrating genetic medicine into primary care)
http://bmj.com/cgi/content/full/322/7293/1027

Increasing availability of DNA based tests and demand by
patients for genetic information and advice mean that primary
care practitioners will need to become genetically literate. A
paper in this week's BMJ discusses the implications of genetic
advances for primary care.

Currently, the most important elements for primary care are
prediction of risk of certain cancers and carrier screening for
common conditions such as cystic fibrosis. Longer term, there
will be increasing use of genetic information to tailor drug
treatment for a wide range of disorders and to predict risk of
common conditions such as diabetes and cardiovascular disease.

Integrating these elements of genetic medicine into primary care
will require the development of generic skills in genetic risk
assessment and communication, explain the authors. A
multifaceted approach - including community genetic counsellors,
primary care genetic specialists, educational programmes and
computer support - is essential to support the procurement of
these skills in primary care, they add.

The authors believe that even if a fraction of the claims made
about the impending impact of genetics on clinical practice came
true, clinical genetic services would be overwhelmed. We must
not miss this opportunity to prepare primary care for the new
genetics, they conclude.

Contact:

Jon Emery, Clinical Lecturer, Department of Public Health and
Primary Care, University of Cambridge, Institute of Public
Health, Cambridge, UK
Email: jde10@medschl.cam.ac.uk


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